The US has a terrible imbalance in trade with Europe, Mexico, Canada, and of course China. Much of this is largely due to the fact that these other countries impose severe tariffs on American products, and so these products don’t get sold there.
What Trump is doing by imposing tariffs is to even the trading field so that the US doesn’t have these terrible trade imbalances. In a real sense, that these other countries are using punitive tariffs on American products forces Trump to do what he is doing.
Trump is a businessman, and businessmen want lots of international trade. Given his druthers, I actually think Trump would prefer entirely free trade — no tariffs at all. But what he will not tolerate are these trade imbalances because, in the end, they make the US poorer.
Trump is known as a deal maker. He sees himself in that light. His book is actually titled “Art of the Deal”. Imposing tariffs is his first move in trying to lower or neutralize foreign tariffs against American products. The second move will be the negotiation with each country on setting up equitable or no tariffs.