If you are a natural US citizen, and your GREs are anywhere close to good, you will waltz into any good Ph.D. program in CS, because there are very few USC applicants who are willing to do the (incredibly intense, shitty, thankless) work required to attain that level of education. This isn't your typical IT administrator stuff...think more along the lines of the nexus of advanced mathematics, systems design, and operations research.
The nationality of admitted students at this level has very little to do with any profit motive either, as almost everything admitted to these types of Ph.D. programs are fully funded (by assistantships that require a ton of hard work, almost slave labor, but still funded). An international student will actually *cost* the university more than a USC, on average.
I am very close to people who sit on the admissions committee at my university...they certainly don't pass over USCs for their health.
The problem with H-1B abuse has little to do with PHd’s. That is a side issue.
Many US citizens stop at an undergrad CS degree for financial reasons, not because they're unwilling to do the hard work for an advanced degree.
Many of them have student debt to pay off for their BS degrees. The last thing they need is more debt. They might want to go to grad school and work toward an advanced degree. But, realistically, are there enough job opportunities, with higher salaries, open to advanced degree holders? I read that most employers aren't looking for people with graduate-level CS degrees because they don't want to pay the higher salary.
Sometimes an employer will supplement the cost of a graduate degree. Otherwise, most American CS majors who stop at the BS degree are being practical, not lazy.