Sorry, but I'm afraid your chances of transferring to a US med school are dismal. There are only one or two students from SGU who manage to transfer to a US school each year, and their grades are impeccable. I suggest you concentrate on getting as great of a Step 1 score as you can, because as a Caribbean student, you're going to need that for residency application.
And why are you so confident you'll get over a 245 on Step 1? A GPA of 2.75, at the very least, suggests you'll have to put in some serious hard studying for the USMLE in order to get a competitive score.