Many things cross US/Canada/Mexico border in the process being manufactured. And tariffs will stack up.
Many advanced products (tech/chip, etc) are not entirely made in any single place. Some stuff is imported, and some is exported again, and tariffing the world, will also make the world tariff you.
I think this is all around bad. Best case scenario the US has elected a president who decided to burn all political capital, alliances and credibility in search of a slightly better deal.
Doing this sort maximum pressure economic extortion style policies, *might* getter you a slightly better deal. But at what cost?
Can EU countries buy US military equipment, when it turns out that the US will withhold support for equipment we've bought and paid for, in order to pressure a democracy, fighting for its existence, into surrender.
Trump may get a win in the headlines, because everyone thinks he'll go away if he get a win.