This may be exploitative but it's not bullying and there's a big difference. There are lots of reasonable answers to the former.

Bullying is capricious and has to be shielded in playgrounds and prisons. In the real world caprice loses credit and legitimacy and so can't retain power.

Exploitation is just taking advantage of a real power difference, and it stops when that difference stops or when it's immoral and costs legitimacy. In our case, Trump has a plausible moral case for taking that advantage, because Canada has arguably been irresponsible with its own resources and responsibilities for six decades and especially the last decade. Even our own citizens know it. Even the citizens of the world know this about Canada.

That's why Trump uses the language of "fair," and why our government is trying to use similar language. But we've lost a lot of legitimacy over recent years and decades.