The US is not the country, nor do they have the reputation in front of the public that led to the Manhattan project, where the greatest minds would willingly work on defense projects, not just willingly but eagerly.
The breakthroughs are also less than they used to be. We have the nuke. We have reached space. We've hit the peaks. Everything else is just automatic turrets and AI to choose who to kill.
I remember being in college. I went to a top CS school (perhaps the top CS school), and it was often considered a black mark if you went to work for a defense company (even Palantir). It was also a different time, when we had our pick of companies to work at, not like today. But that sentiment is hard to shake off. I'm not convinced it is not still large in academia and the CS world today