The United States must manufacture its own weapons inside the country. To do otherwise is suicide.
We'd end up with an approved (short) list of enemies with whom we could go to war.
Further our most advanced technology would be physically outside of our control so that even if we weren't at war with the manufacturing country, another country could invade it and seize control of our weapons source. Then, they'd have our best with which to kill us.
Our days as a free country are numbered.
there is no way to stop the outflow of tech given our current trade policies.