The core idea of tariffs is to offset the price of local production to make it more cost effective to purchase locally.

They are honestly most effectively used when you have a production base that is considering a move elsewhere for costing reasons. Enacting the tariff means it wouldn't be as profitable for them to undertake that offshoring exercise.

When you lack the productive capacity to source a product locally, you need the tariffs to be high enough to make building local productive capacity seem appealing. That is going to create inflationary shock in the short term. The chances of it working for that end are mixed. There is a lot of assumption surrounding how businesses will act. It is essentially gambling that a business is going to prioritize the American market. That's a riskier and riskier gamble as more and more Americans find themselves without money to spend.

In either case, tariffs are a regressive tax. Meaning that lower incomes are more heavily impacted by it.