Beyond a certain point, the tariffs become meaningless because nobody bothers trading legally anyway.

I don't know where the real cutoff is, but for an extreme example: if the tariffs are 1e6% or 1e7%, nobody's buying anything by lawful channels.

Also, there's not much stopping people from shipping to a country with a 10% tariff, that 10% country taking a 1% cut to slap a different "made in" label on the side and then re-exporting to the US, making it effectively an 11% tariff for whoever originally made it.