Clothes are nowhere near as heavily automatable as people like to believe they are, is the problem. Unlike many other goods, nearly every article of clothing produced today is still produced with human hands. This does not mesh well with the fact that the modern public has been trained not to value apparel; people expect to casually buy items of clothing for less than they'd spend on a single meal.
It's not like the cost of clothes would be that much more if produced domestically though... the difference is the margins would be lower, a domestic employee would have a job and the domestic economy as a whole would be stronger as a result. Not to mention, the lower margin also means the wealth gap would be more narrow and there would be less incentive to stoke the flames of class warfare.
Why do people assume that clothes (and other goods, mind you) produced in the US are a mere hypothetical? There are plenty of brands that do so, and your general public overwhelmingly ignores them (and, as you have just demonstrated, don't even know they exist) precisely because they are way more expensive than consumers have been conditioned to believe that clothes should cost.
For instance, actual MiUSA jeans from companies like 3sixteen and Raleigh Denim retail for ~$200+, which is a far cry from the $30 to $50 that most people think jeans "should cost" (and that companies like American Eagle, who have long since outsourced their manufacturing, are happy to provide). Sure, it's not as if MiUSA jeans HAVE to be a few hundred dollars (I believe there are some Gustin's jeans you can pick up for $120 or so), and there are offshored jeans like Levi's which are already overpriced. But you'd have to be very naive to think that there would not be a massive and quite frankly unbearable sticker shock for the vast majority of people if you were to somehow force all domestic clothing demand to be met through domestic production. You could maybe sell it with some very effective austerity propaganda, but good luck with that.
Where did I say there are no clothes produced in the US? That said, I do think there's room to compete of most US clothes were produced domestically and that the pricing could come well below the existing US brands.
There's also brands made in China for cheap with Euro brand labels attached that sell for several hundred. Cost is not the same as price.
