It's not just all about defence. What's sad is that it was for a very long time also an understanding that there's been shared culture, participation as democracies in the world order.
It's become clear not just last night, but with Vance's attacks on Europe (unless they were the European far right parties) that the US's intention is now to try and fragment and dominate Europe.
There is of course no way we'd get 27 countries to agree on everything, this is not at all the point, its going to be a slow process but worth the building.