I assume you're referring to the U.S. "security" rules (background check, fingerprinting, etc.) for flight training of non-U.S. applicants.
I could be wrong, but I don't believe simply adding a float rating falls under the (onerous) background check/application rules for non-U.S. citizens in the States. You should check with whatever flight school you might be in contact with.
That said, it wouldn't surprise me that Canadian procedures are quite a bit simpler.