So this question if fundamentally flawed. The US has one of the largest manufacturing bases in the world. We make PLENTY of stuff, it's just that we COULD make infinitely more and take over from china and other foreign countries. The US based Automotive manufacturing market alone is worth anywhere from 250 billion up to 700 billion a year depending on if you only count OEM parts or if you count aftermarket parts as well.

And that's not getting into Aerospace (which legally HAS to be made by native manufacturers thanks to national security regulations), medical supplies, industrial products, etc. And I'm just talking metal parts so far. We haven't touched wood (paper products), pharmaceuticals (We make A LOT of pharmaceuticals, the problem is the API, applied pharmaceutical ingredients, used to make drugs are almost entirely made in china and india so we have to import them to make said drugs), oil and petrochemicals (we have THE LARGEST petrochemical market in the world bar none. China and others lump in their gasoline production with their petrochemical markets to fluff numbers. The US is the largest actual manufacturer of all the industrial chemicals that make the world run), food and food product production, etc. etc.

We make a crap load of stuff here. The problem is, and this is what Trump is getting at, we could be making MUCH MORE still. Instead of just making certain parts, we could have the entire supply chain be domestic. We could have semiconductor foundries and undercut Taiwan (who makes 90% of all semiconductors on the planet). We could make iphones and computers here instead of in china and india. We could make clothes and tools here in factories instead of outsourcing them.

The US has the means and ability to make EVERYTHING that we typically import. The sole reason we don't is that it's cheaper to import it than to make it domestically. If we eliminate that sole incentive to outsource, then onshoring production is the next natural step for all these companies. And once they invest billions, tens of billions, hundreds of billions, even trillions, in domestic production in the US, they're not gonna just shut it down even if tariffs are off the table. Because now they have all these domestic factories that, while more expensive to run, also eliminate 90% of logistical costs and often will allow for cheaper materials since they can source them domestically in the US instead of having to ship them in from all over the world to some third world factory.

This shifts the power from China and India to the US in terms of being the worlds manufacturing base. It's easier to ship from the US than anywhere else on the planet since we have easy access to both major shipping routes (atlantic and pacific) on either coast, AND if you're dealing with US made goods, you have the safety and backup of the strongest navy on the planet making sure your routes are safe and secure. It ALSO protects you from tariffs and customs. If you're shipping directly from the US, then you deal with tariffs based on the US, instead of china. Meaning when the US drops all tariffs after the deals are made, it's basically free trade between allied countries (which is most of the planet).

Finally, and this is the big one. Most manufacturing companies have WANTED to do this for decades now. China and India are cheap yeah, but that's literally all they have going for them. Both are politically unstable countries, one of which is literally communist (meaning they can just nationalize all of your assets and declare you no longer own them whenever they want, which they've done before), and both are known to have rampant corruption at every level and have a problem with things like IP theft. If you put your factory in either country, you're running the risk of someone stealing your IP and selling it to a competitor. You don't really have any of those problems in the US, in fact you have active protection AGAINST most of them. And yes I know we have corruption, but nothing like China and India.

The sole reason they haven't done so up until now, is that shareholders don't like when companies take on large scale products unnecessarily. Odd I know, but its true. Unless it's deemed an absolute requirement, typically shareholders punish the stock of public companies if they start taking on large scale multibillion dollar, multi year projects. So it wasn't feasible for anyone to reshore production in the US until Trump more or less gave them the excuse to do so. The US is typically seen as THE SINGLE MOST stable market in the world. Not only are we the largest economy on the planet, AND the largest consumer, but we're also one of the most stable because we're a democratic republic AND have the most powerful military to ever exist, AND the most heavily armed civilian populace on the planet. We also have basically zero chance of ever nationalizing their assets (even in wartime we typically don't do that, so long as they fall in line with national interests).

TL;DR: We make a lot of stuff in the US. Trump just wants us to make EVERYTHING in the US and dethrone china/india as the world's main manufacturing hub.