Hey yowhatup,
You are NOT considered an IMG with regards to matching in Canada since you'll be graduating from an American school. As long as your school is accredited by the LCME, you will not be considered an IMG. LCME accredited schools include MD American schools, Canadian schools, and Puerto Rican schools. This makes matching much easier. You can match into Carms in the 1st round meaning that there are many spots available to you.
**However, almost all positions in the match are reserved for Canadian citizens/permanent residents. This is true for even the 'IMG positions' which are mostly in the 2nd round. I think McGill might have some positions reserved for Americans..but it's best to check out the Carms website.
The salaries aren't as low in Canada as many Americans think. In fact, doctors in Canada often make similar salaries as their American counterparts. Doctors in Canada are among the highest paid in the world. Also, the health care system is such that you won't have to deal with huge malpractice fees and insurance companies.
With respect to foreigners entering Canada...Canada is very open to foreigners in general. Canada is amazingly multicultural with 25% of the population born outside Canada. HOWEVER, the medical field has become very closed to foreign trained physicians. The doctors in Canada have been able to protect their turf very well by making it very difficult for foreign physicians to work in Canada. However, American trained physicians are not considered 'foreign' and have few hurdles to pass. That means if you've done medical school in the US and are a Canadian citizen/permanent resident then you'll be able to match into Carms without much trouble. Also, if you do an American ACGME accredited residency, it WILL be accepted in Canada. You will be 'board eligible' to write the Canadian board exam and that's all you'll have to write. You don't have to redo training. IF your American residency is shorter than the Canadian one, you'll likely have to do that extra year in Canada. For example, an ER residency is 5 years in Canada and 4 years in the US. The US trained doctor will have to do an extra year in Canada before working in Canada.
In Ontario, the USMLE will be counted as equivalent to the Canadian licensing exams. However, this is not the case in other provinces at the moment. This may change though. This has to do with LICENSING and not MATCHING though. Canadian residency programs don't look at licensing exams for matching. Matching generally depends on connections and letters of reference.
To become an ER doctor in Canada you can do 1 of 2 paths:
1) do a 5 year ER residency
2) do a 2 year family med residency and then do a 1 extra year in ER. This is commonly called a '2 + 1'.
A good forum for Canadian medical students (and premeds) is here:
http://www.premed101.com/forums/
Hope that helps!