"Our Constitution did not authorize permanent foreign entanglements." Worried about the Constitution, are we? Well, it doesn’t authorize standing armies either - yet here we are.

Go for it. This allows the remaining NATO members to proceed with their own defence and more importantly, their own hardware and guidelines. And, to be honest, the US prefers Russia to NATO which makes it inconvenient.

Not going to be all that good for US defence contractors, but they'll figure something out.