There might be national secret-sauce here or there, but the major military contractors are all international. Lots of projects involve R&D spread across multiple nations. Things mostly get dicey when looking at nations that are too unstable to trust (Egypt, Pakistan, etc.), or those that are current rivals (Russia, China).
Is that trusting one's friends or are they too unstable to trust?
Trusting an ally with any version of the F-35 is a big thing. The base F-35 is still going to be a very great fighter aircraft.
Even since resolution there's unprecedented restrictions of maintenance in RAF service, requiring some major components returned to BAe in the US when BAe are a British based company.
I'm on my way out but a quick search seems to show Israel as having the least restricted version, which is a surprise: https://www.wired.com/2016/05/israel-can-customize-americas-...
Some discussion of the Blair era issues: https://www.defenseindustrydaily.com/uk-warns-usa-over-itar-...
Just because Israel is allowed to add additional equipment to the F-35 doesn't mean anything in terms of the F-35 itself. Which, as I said, is the same as everyone else's.
Yes, that's exactly the problem. What if in the future, my country and USA will be enemies? It is not very probable, but so wasn't a prospect of war in Ukraine, for example. You just don't know how things will develop, and if a company want's to be global, it shouldn't directly support a military of a specific country.