I'm starting to panic..

I think the crux of this is to get as much reassurance as you can. So firstly I would ask where in the States they're going to live? There are lovely low crime areas all over America, check out where they plan to live and if it's not a 'safe' area perhaps you could discuss this with your daughter. America has a system that delivers amazing health care (including mental health) for those who have good insurance, so maybe check out whether your son-in-law will have work-related insurance and if not, how they propose to pay for it. Does the neighbourhood they propose to go to have a good community and will your son-in-law's family be nearby to offer family support?
If you can be reassured then it will be easier all round to let them go and your questions will perhaps help them to clarify their own thinking as long as you can appear fairly neutral.

A very valid point made by grannyactivist, the problem with healthcare in the US is not a lack of it, it is that insurance is ridiculously high and there in no real concept of universal healthcare like you have in the UK. If your son has a good job in the US waiting for him, with a strong health packet thrown in, it might be a great thing for them.

All good points from grannyactivist I think you should talk about the health care issues given your daughter's medical history. As your son in law is American I'm sure he will have given this some thought.
Like all countries there are high crime areas, anyone not in the UK would think we are all knife wielding maniacs so get this in perspective.
My daughter married an American as well and went to live there. They had a great life with their children in USA until sadly he died.
Don't put unnecessary doubts in your daughter's mind they could have a great life there.

It seems slightly strange to want to move continents because their catchment secondary school is naff - most people just move up the road.

Also, the quality of schools varies over time, depending to a large degree on the head, who may have changed in the next 6 years.

OP’s daughter and sil are only ‘considering’ the move. As Grannyactivist and others are pointing out there are many aspects to assess.

MiniMama - best to keep a distance, don’t bring the subject up yourself and try not to worry, it may never happen.
Just offer your daughter the support you have no doubt been providing all her life.

I’m a bit puzzled about the apparent assumption that American secondary schools would be any better!

AbsolutelyGrandma70s

Hmm this whole plan to move sounds a bit scatterbrained and illogical for the reasons given. Are you sure they weren't just daydreaming out loud? I bet it comes to nothing.

Don’t forget that ( hopefully) your daughter will also have the support of her DHs family and friends.

Be supportive and start saving to go and visit, on the other hand they might just be looking at all the options.

A very important issue for them to consider is health care for all the family. What sort of cover does her husband have, is it linked to his job and if so is it a stable job? If you have good health care the system over there is far superior to the NHS, ie shorter waiting times and hospitals over there are far superior to ours. I was hospitalised for 11 days when in Florida a few years ago, I had an en suite room, the nursing care was wonderful as were the doctors and physiotherapists. The picture is very different if you do not have a good healthcare package.

Another issue of course is schooling for the children. Some schools in the USA are very scary places, they need to do the research.

As sodapop said you can have a great life over there but it all rests on whether you are financially stable.

Several members of my close and extended family have moved abroad, including to the United States, and sometimes permanently. I think that, without exception, it has been the making of them. Facing up to new challenges has made them stronger, more resilient people. You must let your daughter make her own choice, but, if she goes, be sure to set up appointments for regular meetings on Skype or similar. And, if you can, start saving for the fare.

So many many things to consider first. Has she stayed for any length of time in the area they may want to live? Does she really like it? There would have to be more than one reason to up sticks and go so far. There are ropey and underperforming schools everywhere. Similarly there are great schools everywhere.
Plenty of things to talk about here!
As others say, if you try to remain neutral, you can help her explore the possibilities and pitfalls.

Marking exams from abroad, including the States, has taught me how superficial and limited their education system is. I wouldn't let my children be reduced to the education system in the USA.

I think grannyactivist has covered the main points for consideration, and a few others have added to that.
What I would be most concerned about at this stage, is would your daughter, who has endured so much already with Post Natal Depression, be able to cope both mentally, and physically, without the nearby support of her parents? Especially as she has only just come off the antidepressants. That would be my major concern, as I have a daughter who has suffered PND and I know firsthand how much support is required in this situation.

In addition, I was not aware that the education system in the the USA was ‘better’ than what is offered in the UK, in fact, if anything, I thought it wasn’t so good.

Agree Mandyone

MiniMama I think you've fallen into the trap of extrapolating the news to the whole country! Yes, people have guns and yes, there have been tragic shootings but the US is a vast country and 'mostly harmless' (to quote the Hitchhikers Guide). As OP points out, if it's with your SiL's job then he will probably have health insurance and I'm sure the mental health care is as good as, if not better than, here if they can pay. Does she want to go? Is it him pushing for this? Could they come back if she can't cope?

I would be a bit worried that she thinks she can escape her problems by going to the USA. And unfortunately they will follow her. On the other hand she might flourish in a new environment.
At the end of the day it's their decision.

MiniMama.Many of us have to watch our children fly to a different life overseas and I endorse what Matelda says. Each state in the USA varies but I have nothing but praise for the education and medical treatment my family have received since they moved to that country taking my grandchildren with them. Children, now adults, making their own way in a country that, contrary to the doom mongers, have many opportunities there for the taking. No they don't have a NHS. People take out insurance but I can assure you there are those in the U.S who do receive benefits depending on their circumstances. The U.S reward those who help themselves and you cannot condemn something unless you have had experience of it. As for the crime rate comparison has to be made when you measure the size of the US to the UK. Yes they do have easy access to guns however the UK is not as safe as we would like it to be. I can understand your concerns I have been there but don't let your daughter see these concerns. Give her your blessing and what would stop you from experiencing what that country has to offer your daughter once she has settled.

Say nothing. Your son in law is American. It is not as if they are going to a country where neither are familar with the health care and education systems. His experience comparing what the two countries have to offer must have had a bearing on their decision. I doubt local senior schools are the prime reason as there would be closer solutions. If your daughter seems happy with what she and her husband are considering then you have to let them go ahead without interference. If she needs to know and plan she'll be doing her homework. Sometimes a change of location and a new start is just what we need to get past difficult times.

Good advice here and follow grannyactivist.
The media tend to make us think everything is bad in the US but that is just so far from the truth. There are many Brits who have emigrated to the US and loved it.

Your SIL is American, and it is quite natural that he might want to move home and give his child the kind of upbringing he had and his wife the kind of home he grew up in.

Presumably, he has family he misses? Perhaps this, and not secondary schooling, is the real issue.

In your place, I think I would have a quiet word with SIL concerning health care in the US and a quiet word with DD pointing out that the school system is definitely not better in the USA than anywhere in Europe or the UK.

After that you just have to let them make up their own minds, and it does depend a great deal where they intend to go, how worried you need to be.

This is what Google says about gun law in the States

All 50 states allow, at some level, concealed carry, but some states are considerably more restrictive than others. California, Florida, Illinois, Texas, South Carolina and New York (as well as Washington, D.C.) are the only states to prohibit open carry of handguns in public.20 Nov 2014