American First is a very parochial viewpoint, largely uncaring of happenings beyond US borders. And this is precisely what Trump, all MAGA, and a lot of Republicans believe in.
Who cares what happens in Europe? - doesn't affect me... why are we spending money to fund NATO when there's so much poverty in the USA?... and so forth. That's the mindset that will shortly run US government for the next 4 years.
Where's the hawkishness gone? It's been mostly voted out of office, with of course, some exceptions.