I can't forge metal but I feel like my forks in my kitchen are mine because I can operate and maintain them until they fundamentally break. I do think that's ownership

But I agree there's more than one way to view ownership and I can see your point, even if I don't think I agree so long as the UK can truly operate it in every way, including software that might need adapting (like how I might bend my fork's prong back into shape, or out of shape for adaptations)

For forks fine. But military equipment breaks all the time. And the maintenance requirements on things like jets are 4:1 or greater. So having a jet down because a part is missing and not able to be supplied is a real issue.

Can the USA make every part of the F35?

https://www.czdefence.com/article/europeanisation-of-the-f-3...: “The F-35's manufacturer, Lockheed Martin, states that currently around 25% of the F-35's components are manufactured in Europe.”

That doesn’t say the USA cannot make every part, but I think it’s likely they will have trouble producing some of them.

For example, https://simpleflying.com/how-many-international-parts-us-f-3... states the F35 has Martin Baker ejection seats and the F35B has Rolls-Royce engines.