Is this super strand of staph infection being brought to the U.S. by illegal aliens?

I can not say that it is for sure but it would not surprise me. If you immigrate to the US legally you must undergo medical exams and tests for diseases. I highly doubt Mexico has a real concern for health of their citizens. One problem is also over prescribing of antibiotics. You are incorrect on Europeans infesting Native Americans with disease, I suggest you read "A Patriot's History Of The United States", by Larry Schweikart and Michael Allen. It covers the history from the discovery by Columbus to the War on Terror.