Most of your trade with the US consists of raw materials (oil, gas etc..) I doubt any strict border control would have any siginificant impact on that section of the economy.
The nice thing about oil and gas is that we can sell them anywhere. That would have a significant impact on our economy because we get more money for them on the international market than we can selling them to the US under NAFTA. You can toss potash in there too...you guys can't farm without it.
Your trade with the EU and Pacific Rim has been declining even further over the years.
It has, and yet we know how to get it back. China is buying oil and pre-fab houses from us. Japan and the EU will buy our beef if we start testing every cow. We've kept GM wheat out of the country, so we have vialble markets for it all over the world. South America, Asia, and Africa are all interested in Canadian technologies ranging from water purification to alternative energy.
The Canadian and US economies are integrated heavily.
Our fixation with the United States has made us vulnerable. It's time we changed that.
Given the debt crisis in the US, being too closely tied to the US economy is like playing Russian roulette.
For example, the soft lumber issue recently, Canada exports most of its soft lumber to the US, the US exports heavy machinery for the timber industry to Canada, so in this case we both lose. Just as the EU countries are heavily dependant on each others economies, so is the case with NAFTA.
NAFTA was designed to benefit multi-national corporations. It is not good for the people of the US, Canada, or Mexico.
I don't pretend to understand everything about economic data, but I would assume if the Canadian dollar almost evens out with the US dollar, at that point your products would become more expensive in the US and that is where your economy would be hurt mostly.
It wouldn't hurt those aces I mentioned at all. Those are cheaper than on the world market and will remain so as long as we under NAFTA. Even without NAFTA the transportation costs are minimal, so even at world prices and without any subsidies whatsoever they would remain cheaper.