The US is by far Canada's main trading partner, with 66% of Canadian foreign trade being with the US. It exports 17 times as much to and imports 4 times as much

The US is by far Canada's main trading partner, with 66% of Canadian foreign trade being with the US. It exports 17 times as much to and imports 4 times as much from the US than its next largest trading partner, which in both cases is China. Many companies operating in Canada are American owned, and many Canadian companies have a significant presence in the US as well. The Canadian financial sector is heavily integrated with the US. Canada and the US are close military allies. They share the world's only binational military command (NORAD) which is responsible for air defense of both countries. Canada has joined many US led military operations including Korea, Afghanistan, and both Gulf Wars. The US strongly influences military procurement in Canada, with Canadian units designed to be seamlessly interoperable with US forces. The US and Canada share the world's longest border, which is rather porous. Large numbers of citizens of each nation travel to the other frequently, and many people have family on the opposite side of the border. Many Canadians live for an extended period of time in the US for education or employment. Basically any economic, military, or immigration policy change in the US is going to have a huge impact on Canada.