I was surprised at all the comments from people who seem to not understand how tariffs work. So here's a more concrete example. (And for those who do understand, forgive me):
Say the government decides (as it has in the past), that it's tired of Americans buying foreign cars. There's two ways it could bribe people financially to change their behavior:
1) The carrot: If you buy a Corvette, you can deduct the entire price from your taxable income. Better yet, you can get a full tax credit for your Corvette - literally sending your Federal tax dollars to Chevrolet instead of the government. Result: many more people will buy Corvettes*, Chevrolet will hugely prosper, those Americans who do buy Corvettes will have an ultra cheap car and have more money to spend, the economy goes up. Those that love BMWs can still buy them as before - they just won't see a positive increase in their income.
2) The stick: If you buy a BMW 3 series*, you will be charged an a $20,000 penalty. (The Tariff). The result? Some Americans may switch to buying a Corvette. Chevrolet may see some boost. Some Americans will pay super high prices for BMW 3-series cars. Many Americans will no longer be able to afford a BMW and will just buy used or hold on to their cars longer. BMW may lose a little business, and Chevrolet may gain a little business, but Americans lose cash, and the economy suffers.
BUT: the intended benefits of Tariffs (to promote domestic industry) only work when there IS a domestic alternative. Imagine this same scenario, but pretend the US HAS NO CAR COMPANIES. So the government just says "buy a foreign car, pay a $20,000 penalty." This costs foreign car companies some sales, as before, but it mainly just makes Americans poorer, because in this example there's no local car they can buy to avoid the penalty. It's now simply a tax on new cars - making them unaffordable for most people. And the economy goes down, or the quality of life measured in the state of the car you drive, goes down.
This was an example from the consumer side of things, but it's the same scenario from the seller side of things - you're just applying the penalty to the businesses, who have to pass it on to the consumer. In this example, "Any car dealership that sells a foreign car must pay a $20,000 penalty for every car sold." It doesn't make a big difference where in the chain it happens, because everyone will try to pay part of the tariff to try to reduce business losses.
This was the big flaw in the Brexit argument: People who were pro-Brexit said "Europe is a huge trading partner who can't afford to lose us." But what they overlooked was that while England got a huge fraction of its goods from Europe, Europe only got a small fraction of its goods from England. So whatever hurt that trade hurt England far worse than Europe. It's a Pyrrhic victory - we'll nuke ourselves to cause you a little inconvenience.
* I just picked Corvettes and BMW 3 series as classic proxies for American and Foreign cars. I think they're both cool - no insults intended.