What is the best U.S. College Savings Plan for a retired 52 year old American, without a pension, to invest in for a seven year old Mexican student that will enable him to attend college in the U.S. or in Mexico, as he determines in the future?

I understand I cannot open an Educational Roth IRA since I am retired, and a 529 Plan would require a U.S. state school, correct? Any other suggestions?

Thanks. Susique76