Why did he threaten 100% tariffs?

He did not like the Canadian prime minister's speech about "great powers" weaponizing economic integration, so he decided to prove him right.

Because Canada has been in trade talks with China and may potentially lower its tariffs on China which gives them a back door into the US. There are some specifics and it's all conditional. It depends on the kinds of deals it settles on.

It's not a back door to anything. It's competition for the US and Japanese automotive manufacturers who are protected by the existing tariffs.

It's multiple things. Yes, the automotive manufacturers matter not just for business sense, but because manufacturing base is important to be able to leverage in case of a war. Manufacturing lines played key roles in WW2.

In addition to that, since we're on the car angle, Chinese EVs are basically just privacy nightmares. I mean, all cars are at this point, but that's why we definitely don't want Chinese ones coming across the Canadian border and ending up all over the place.

In the end there are in fact legitimate national security concerns that the tariffs address and Canada risks weakening those. So, that is the actual answer to why.

With NAFTA/USMCA it 100% is a backdoor. China couldn't give a rats ass about Canada the purpose of these proposed trade deal with Canada is to bypass USA tariffs into the USA market.

No it is not. Canada did not try to do anything resembling Free Trade with China. It is btw prohibited by NAFTA / CUSMA. Canada pursues reasonable targeted deals like every normal country should. Trump is just getting hysterical because some country does not want to suck his dick. He should learn to be civil when dealing with neighbors, well it might be too late for that.

prohibited by nafta/cusma isnt particularly important. the US already ignores the parts it doesnt like

canada should have a free trade deal ready to go for when the US pulls out of it altogether

I do feel as why demands reason and I am not sure if you can reason with the unreasonable which is what the Canadian speech was about in Davos and then POTUS threatened 100% tariffs again.

Kind of proved the point of America being an un-reliable partner which is what I inferred from Canadian PM's speech & his call for middle economies to connect with each other and strengthen together to have more leverage overall.

Because after the US threatened to destroy our economy and/or annex us by force and/or cancel nu-NAFTA and/or impose tariffs on us regardless, we realized that Americans don't actually want us as friends so we started diversifying our trade partnerships and negotiated a mutual tariff relaxation deal with China.

The previous Canada-US relationship is gone. Months ago I wrote on HN that purely by virtue of having to weather this storm, the nature of Canada-US relations will be irrevocably and fundamentally altered. Even if Trump and his cronies were jailed tomorrow, it's too late. The rest of the world understands that Trump is just a symptom of the disease affecting America and it's going to get worse, not better.

Delusion? Dementia? Being surrounded by yes-men?

Probably bummed because nearly everyone (rightfully) praised Mark Carney's speech in Davos (in contrast to Trumps incoherent ramblings). I am pretty sure he can be that petty.

> Canada is (was?) the single biggest commercial partner of the USA

It is "is" and it will continue to be is probably for the rest of Canada existence. You can't trump geography here and frankly Canada's decades of under investment in shipping infrastructure means they need to use USA ports for foreign trade anyway.