"What a contrast to Canada, where the two major parties, which disagree on so many things, are both still pro-trade."

That's one way of putting it. Truly, what you have is two parties dedicated to neoliberalism, market fundamentalism and making the country's laws and tax regimes safe for rich people. 

Indeed this is one of key reasons why both Liberals and Conservatives favour FPTP, which is a system that empowers brokerage politics that favour the wealthy and their political stooges and that disempowers democratic movements dedicated to leveling the playing field and making the rich and the corporations pay.