Hello Soontobe well a lot has been happening on this thread since I was on early this morning.
You asked me two questions so here goes. From my experience self publishing generates very few sales because there is no one out there to see your book unless you make great efforts to promote yourself, especially if it is on Kindle as opposed to hard copy.
My friend got a local charity shop to allow her to launch her book, but of course you have to try and get folks to attend the promotion and more importantly buy the book.
Even with established authors like my DS his publisher expects him to do some self promotion so this year he is touring on and off for 12 weeks to schools/ festivals in the UK and abroad. I only tell you this so that you realise that very few, if any, authors can survive without doing self marketing. The publisher provides posters, bookmarks etc but my DS distributes them predominantly himself.
I really don't want to be negative but breaking into the USA market is notoriously difficult, even though I agree with you that the subject of your book may appeal to Christians over there. Perhaps you could send some copies of your book to some church groups in the US, just a thought.
Don't let me put you off writing, you could be the lucky one whose book takes off.