Japan has no problems making US equipment. Basically nothing comes across that is entirely US made.It will be interesting to see if EU members and EU defence manufacturing will fully commit to an integrated defence. As for American companies being locked out, probably unlikely unless military kit production is really ramped up along with solid R&D. if the US wants long term future EU business it will have to do what the US makes EU vendors do, make the stuff locally.
The Koreans are the same. Almost nothing is purchased wholely US made.
Both made big booboos with the F-35. I think they thought they would have to commit to
But the Japanese are smart. They order actual volume of stuff, so they get some scale of efficiency. But they don't have to redesign every military item from scratch.
I don't think the Americans have a problem with the EU licence builing thousands of copies of equipment. As we are finding out with AUKUS. Most American manufacturers only want to deal with American military spending, not look after volatile overseas buys.