China has nukes, a gargantuan military with no other purpose than to fight back, and the internal cohesion to resist the pressure. Canada has a much smaller military spread out much further, a much higher dependence on US specific trade simply by nature of physical infrastructure, and an unfortunately not insignificant percent of the population in the central provinces who would probably side with the US. It’s not anbout fighting back, it’s all about who is easier to bully, where friends mean nothing because everyone’s worth is determined by how much he can exploit them and the leverage the us has over them.