Either I am misunderstanding you, or you have it backwards.

America exporting less would result in a larger trade deficit, from America's pov.

If exports are 10, imports are 20...

10 - 20 = -10

Trade deficit is thus 10.

If exports drop to 5...

5 - 20 = - 15

Trade deficit has increased.

You would either increase exports, or decrease imports, to balance a trade deficit... which is, very simplistically, what tariffs try to make happen.

But, a basic macroecon course will tell you that all that does is make everything more expensive for everyone, a lose-lose situation.

Advanced macroecon will tell you there are sometimes good reasons for highly specific, targeted tariffs, coupled with domestic policy to incubate or support a specific industry...

But willy nilly, slapdash, tariff everything?

Just historically verified to blow up every large, developed economy that implements them.