I don't understand why so much weight is given to the difference between US and non-US nationals. And in my experience, it's pretty common to see the US assign

I don't understand why so much weight is given to the difference between US and non-US nationals. And in my experience, it's pretty common to see the US assign a pretty high amount of trust by default to US citizens. For example, a few months ago I visited a friend there, and I got to tour the SpaceX factory. Since I'm foreign, he had to jump through some hoops and there were parts of it the factory that were off-bounds for me. I know there are very tight controls on space-related industries and I can understand the no-pictures policy, but I don't know why it makes such a big difference whether I was born elsewhere.