> They'll learn how to do it, and when that happens what will the US do?

Continue coming up with even more advanced ideas. This is like the Winklevoss Twins getting mad at Zuckerberg for 'stealing their idea', and the dean of Harvard lecturing them about how they're Men of Harvard and as such they'll simply come up with another idea, because that's what Men of Harvard do. They don't just one and done with one good idea.

The US built the world's most advanced idea factory, but the people who hate smart people got into power and now they're stripping the copper out of the walls.

> And then, in the conflict

There won't be a hot conflict between nuclear powers. Or there will, and whoever can make the most drones will be irrelevant in the first 24 hours.