Hello Chuck,
Your comment that the USA needs its current visa regime in order "(not to) become a haven for terrorists like (our) beloved Canada" assumes the following: (1) that Canada is a haven for terrorists; (2) that the USA is not; and (3) that the USA will not experience any problems if it tightens its borders.
There is little doubt that Canada has a considerable number of undesirables who are left more or less unmolested by the authorities (RCMP and CSIS asleep at the switch once again). However, we're nowhere near as bad as the UK. Further, we don't seem to have people sending letterbombs, or carrying out ramdom sniping, or blowing up federal buildings, etc.: all of which activities have been perpetrated by US citizens in the last few years (note that I didn't mention the anthrax thing, because we still don't know who is behind that).
While I am no supporter of our ridiculous immigration laws, I can't agree that any of your premises are valid. They are particularly objectionable because they implicitly support the common American belief that Sept. 11th was carried out by terrorists who came into the country undetected from Canada: a theory that was carefully investigated by the authorities and was found not the case.