If you attack a NATO member, the largest military in the world responds. The US has multiple of the largest air forces if you count our military services separately. I would assume Trump pulling us from NATO would affect our forward bases, but we may do better than brexit I guess. I just don't see it as likely. But, my point is that our independent and joint military ventures frees up nations with smaller GDPs to focus less on their own defense (even if they contribute more as a percentage) and it's a situation the US military likes.
The US military is bigger than every other military combined, unless things have changed in the last few years.
We build bases and share planes and tech, they let us and save on defense. Our defense strategies involve using NATO bases to fuck up opposing belligerents.
Oh shit. I legit thought this was hex.