It’s a robust rule I’d like to see implemented. Obviously there’s a lot of nuance and important details, some if which you highlighted, but the general idea is, that the goal should be to make a policy that’s “fair” in some way or another, and not just go “hur dur muh free trade” free-for-all. For example, I’d probably give Mongolia a bit of leeway as it’s a poor, developing nation to help them catch up, whereas I think US should be punished mot for the reasons you highlight, but for being a tax haven and maybe even for pollution.

But in general, my argument isn’t about some specific countries, but instead about specific products. A company in Mongolia selling to EU could either not give their employees medical insurance and sell widgets to EU for €50 + 100% tariffs, or treat their employees by EU standards and sell widgets for €100 and no tariffs. The ideal tariffs would exactly balance that (while still allowing Mongolian widgets to be cheaper because of lower wages because of lower cost of living.)

to go full conspiracy theory, standards of fair trade, e.g. labour standards, worker rights, IP etc, exist to cripple emerging economies, to contain their growth and limit their ability to compete. political spin doctors have wrapped this up in the veneer of fair trade, equal standards, to get ordinary people to take the bait.

there are ways to mitigate the growing pains of economic development but to prevent it completely is not a solution. nearly all industrial nations have, at some point in their history, gone through the whole process - discovering necessary safety standards, methods to encourage cooperation and where it fails, enforcement and legal repercussions remedies and punishment, etc... that really ought to be hyper-local and community-specific in their implementation. first world governments are fully complicit in preventing emerging nations from developing this themselves.

Factor those externalties - internalized for some manufacturers by regulations - that allow them to manufacture more cheaply into the import tariffs. Trade is not the same as a tariff-free common market.