A mess. Guaranteed. Will have tons of side effects, most of which will be unpleasant.
Look, we have been here before. We have seen a Trump's tax cut and a few Trump's trade wars and several Trump's tariffs. All of them were the same: messy and full of unintended consequences. In fact, those seem to be the only consequences.
Tariffs in particular were messy. Mostly because they are almost entirely under executive branch authority at this point.
I remember a relatively in depth (I kidded, no, the discussion was super high level as far as these things go) discussion on NPR during his first administration.
Just so you know, tariffs are extremely complicated, even as far as taxation goes. The rate on an item is determined by multitude of factors. For example, how much tariffs, say, a pair of shoes must pay depend on what kinds of shoes they are, where they were produced, how much the buyer is getting that day for that particular type of shoes, etc. it's a freaking complicated things.
And on top of that, Trump administration would fiddle with all of these variables at seemingly random. They adjusted up or down various rates (again, each rate is extremely specific to a situation) for no reasons at all at random period of time.
Also these changes may or may not correlate to any particular statement or pronouncement or tweet of the President.
So the greatest impact of all this is to make life of import-export businesses hell. They could never know what to expect ahead of time.
It's also worth calling out that the modern global economy and supply chains are, themselves, over-optimized over-complicated mess.
Take a plastic packaged fruit, alright? The raw material of the plastic (would be oil) is pumped from the earth in one country, processed into raw plastic casting beads in another, actually made into the plastic container in a third, then shipped to the canning facilities in a fourth. The fourth country may or, often times, may not be where the fruits themselves are grown and harvested. In fact, it's not at all rare that the fruits are grown in one, prepared in another, and finally packaged in yet another. All the while, the ships physically carrying all these trades probably are owned by 1 country, operated by another, while flying flags of a third.
And this is like a package of fruit.
A car, for example, is a massive web of supply chains, from physical parts to the copyright and intellectual properties. It would be imported and exported from a country multiple times at different stages.
Tariffs must handle all that. And businesses must navigate all that.
Back to Trump and his grand idea of tariffs.
What are his tariffs? Nothing at all but messes. Look, even statements like “Trump will raise tariffs on cars from China” make zero concrete sense. What are “cars”? How much must China contribute to call it “from China”? What are timing?
So yeah, that will be what Trump's tariffs: messes.