When UPS charged me a $684 tariff on $355 of vintage computer parts

Tariffs are great. They protect the struggling domestic IT industry and gives it time to ramp up its production of vintage computer parts.

Too bad all the competent politicians were dead set against preventing the "free market" from hollowing out American manufacturing.

I understand your sentiment, but I feel like your position is somewhat simplistic, and the actual situation is more complicated.

First, overall, the US has increased manufacturing output over the last couple decades. 2019 was the highest year ever, covid interupted a bit, but levels are back there again.

However the number of people involved has dropped a lot. US manufacturing prefers automation and prefers to manufacture things which are high-volume, low labor.

A good parallel is agriculture. Foods produced in the US (and the US produces a lot of food) tend towards low-labor. Think fields of wheat or corn, not vegetables. Most fresh produce comes from cheap-labor regions like Mexico (or is grown locally with foreign labor.)

So really your point is not about American manufacturing, but rather American labor.

Secondly, this free market you refer to is the American consumer. They are very price sensitive, and deeply favor cheap over good. This contrasts to a lot of the rest of the developed world which strikes more of a balance in this regard.

Since labor is cheaper elsewhere, it follows that cheap imports are favored (by the consumer) over the locally produced items. Unfortunately the imported good is often of a higher quality now (because foreign manufacturers can afford quality and still be cheap.)

So, the politicians you speak of (regardless of party) are reluctant to medel, partly because of unintended consequences, and mostly because the only real lever they have is to increase the cost of imported goods (ie tarrif them) which in turn gets consumers upset. (Witness the fury of the voter in 2020 because of more expensive goods.)

Thus while it's helpful to blame politicians, politicians are elected by consumers. Consumers who could by local, but choose not to. Consumers who vote against politicians that cause price hikes. (Even when those same politicians incentivise local production with things like CHIPS act.)

You can blame politicians, and indeed corporations all day long, but the consumers are voting with their wallets, and "cheap" is the only metric they care about.