Comment by rjbwork

Targeted tariffs in combination with robust industrial, economic, and monetary policy can be effective in incentivizing certain types of production to remain in, grow in, or return to a country.

Blanket tariffs on entire countries or indeed the entire world amounts to a massive tax increase on your entire populace unless you can somehow start producing everything yourself immediately.

There is an argument that it's primarily being used as a cudgel to give the US an advantageous starting position in trade negotiations, but that seems to be a post-hoc explanation/justification.