Just because someone has a Masters does NOT mean that they didn’t go directly to a doctorate. At some universities, you’ll get a Masters after two years of your doctoral work at which point you’ll pivot to heavy-duty dissertation and either research or teaching to justify the financial support you are getting from the university.
That doesn’t mean that people who graduate from Berkeley need to do “remedial” Master’s work to enter a PhD program.
And yes- not having a US passport (and being unable to get security clearances as a foreign national) is definitely going to make landing a research spot more difficult.
And half a dozen rounds of interviews is not terribly onerous… the PI wants researchers who are excited by the project and can contribute. The student wants to be somewhere which will advance their learning. You can’t establish that in a fifteen minute zoom.
But a student visa-- and no security clearance- that makes it hard for sure. And going to Caltech won’t make those two issues easier. Labs at and near Caltech do a LOT of defense and national security work in CS…