Canada also could turn off the power that goes over the border. Americans not being able to charge their phones to watch more TikTok will probably do the trick.
countries will not want military bases from a nation that threatens annexation, will not want their media companies broadcasting to their citizens, will not want to buy their weapons, and will not want their financial system dependent on them
the US just handed the world to the Chinese
on a platter
annexation of Canada would trigger Article 5 against the US