If you have no money to pay for college right now, will you have a lot more money in a year? McGill is an excellent university, but the most famous universities in Canada (McGill, Toronto, UBC) are significantly more expensive for international students than many of the other universities in Canada, and there are a lot of other very good ones to choose from.
You can ignore this comment if you are a Canadian or French citizen, in which case McGill would be very reasonably priced.
I know someone who transferred into McGill years ago from a US university, and who told me that he did mostly get credit for his courses at the US university. This was however a long time ago and the admissions staff at McGill would be better able to tell you what credits you might get.
If you have really good stats and no money, you may be much better off taking a gap year and applying to one of the places that have automatic full tuition and full ride scholarships right here in the US. Go read the thread on that topic at the top of the Financial Aid Forum. A few of those places are still accepting applicants for the coming fall, so you might even have a good place to go sooner rather than later.
Unless you will suddenly have money next year none of these are affordable for you, as they will all be north of $45K/pa, with only the $5500 FAFSA loan available for finaid:
St. Andrew’s University, King’s College London, UCL, Oxbridge.
University of Luxembourg is affordable, but I doubt that they will take any transfer credits. Be sure that you have looked carefully at the course descriptions: there are very few electives. IF they accept any transfer credits it will only be for courses that are clearly substantively equivalent to required first year courses.
Sciences Po explicitly does not accept any transfer credits.
With high stats, getting accepted will not be an issue except for obviously Oxbridge and perhaps Sciences Po (they do an interview), especially for the Paris campus.