A tariff can be helpful if, for example, the Chinese government decides it wants to dominate the world market in widget production and so subsidizes the production of widgets by Chinese counties. This has happened in the past with steel.

But the downside is so much worse. And we experienced it not that long ago. Good read is here: https://www.ers.usda.gov/amber-waves/2022/march/retaliatory-tariffs-reduced-u-s-states-exports-of-agricultural-commodities/

Basically, the US applied tariffs on a bunch of stuff from a bunch of counties. The stuff we bought produced in those counties or made from things produced in those countries became more expensive. (I remember washing machines becoming substantially more expensive as a result of the tariff since I had to buy one at the time).

But that’s not the end. Those countries applied retaliatory tariffs to stuff the US exports - mainly agricultural goods. Those things are commodities produced by many countries, so a bunch of them simply stopped buying the tariffed US products, and instead started sourcing them from places like Brazil. I’ll leave it an exercise to the reader to figure out whether there’s a link between US tariffs the accelerated destruction of the Amazon rainforest to satisfy sudden new demand for produce.

And here we are years later and while many of those tariffs are gone, the US agricultural industry never recovered much of that lost business.