My first reaction was to be a bit pissed off. But then I started to think about it more, and realized that the US concerns don't have to be valid. It's the right of Americans to tighten up any of their national borders for any reason.
Some Canadians believe that the northern border states won't allow the new passport law to come into effect, but given that Canadians are far more likely to have passports than Americans, it will benefit the border states to make it more difficult for US tourists to leave the country.
It's part of the post-9/11 world that the US has changed, and instead of wailing about it Canadians should accept and adapt. In this case, it seems that the only solution is to strengthen our east-west ties (Asia and Europe) and loosen our north-south ties. If we don't, we're possibly in for big trouble down the line.
As Walt Kelly said, "When you starve with a tiger, the tiger starves last."