Don't mess with that. They mean the country that sponsored your J1 and that you signed as 'country of last residence before entering the US'.
Common scenario:
--Physician from india
--residency in US with letter of need from india
--goes to canada for locums/fellowship, obtains canadian PR (fairly easy at that point)
--tries to return to US after 4-5 years on H1b or tries for GC
--Gets bitten into behind by unfulfilled foreign residency requirement
(If you read the wording of 212e, you could interpret it in a way that you can return to the US from canada 2 years after you have become a canadian citizen, that means 3 years after obtaining PR and living in Cdn. But I am not sure whether USCIS reads 212e the same way, I doubt it.)
One way of going about it is by getting canadian PR before you start residency in the US. It takes money and planning, and without the 'work experience' points it is a lot harder. But that way, you can try to get 'health canada' to sponsor your J1 and you would be able to go to cdn after a residency in the US. The bottleneck for that idea is probably 'health canada'. While I think that they have softened up on the issuance of J1 support, I don't know what their current policies are.
If you can bear to read through 32 pages of canadian buerocracy lingo, here is the policy for anyone interested:
http://www.hc-sc.gc.ca/hppb/healthcare/pdf/requirements2005.pdf