I don't know how it works in the U.S., but in Canada, voter grievances have been known to shift political power. And unlike the U.S., Canada is not effectively a two-party system. And Canada in some cases leans toward responsible government (as opposed to simply representative). In a case like this, it wouldn't be yet another order of the day.
NDP condemns Harper's push to sell out Canada:
“The previous Liberal government engaged Canada in a slow merger process with the United States and Stephen Harper is accelerating the agenda,” said [NDP Trade Critic Peter] Julian. “The NDP demands a full debate in Parliament on this issue. Everyday Canadians have the right to know what is being negotiated.”
[...]
“Canada is not the gas tank of the United States. NAFTA already locks us into supplying energy to the United States even if ordinary Canadians go without; a North American Union would only make this worse,” said [NDP Energy Critic Dennis] Bevington.
“Canadians should know that the SPP process supports a North American Union (NAU). The NDP rejects the secretive process surrounding these ongoing discussions. Canadians will never support a political ideology which aims at turning North America into a fortress for corporate interests and neglects the interests of ordinary Canadians. Canadian sovereignty is not for sale to the highest bidder and the federal government has no authority to push for a NAU without a mandate from Canadians,” said Julian.
Either way, it still doesn't change the fact that it is a bad idea.