Are you American and can only consider the goal to be to make profit? Consider the possibility of the goal being to cause economic pain for the US.

You admit the US bonds are currently in a precarious position. All the more reason why putting $450B worth of them onto the market would be effective in causing economic pain for the US. Sure Canada would lose money, but we’re going to lose a lot of money from this trade war anyway. I’m sure this would be considered like a nuclear option, only to be used if the US starts getting too crazy.

Besides, Canada will be making some money with the sale of bonds. That money can be used to offset the negative impacts of the tariffs. So US consumers pay higher prices while US government will pay higher interest on their debt so Canadians will get financial aid. Canada will transition away from US trade, while the US will decline.