I applied to the US as a Canadian with a bachelor's degree from a Canadian school. It's not a problem. AAMC accreditation is not nessesary. The AAMC only accredits medical schools, this has nothing to do with the undergraduate studies at those same universities. There are universities in Canada that don't have medical schools and thus could never be accredited by the AAMC, but a degree from these schools will be accepted for US med applications.