That would only be conceivable if there was a single domestic manufacturer. You don't need a foreign product to keep prices honest in a competitive domestic market.

You do, actually. Countries that have succeeded with tariffs to "build an industry" eventually forced their companies to compete in the foreign market (look at Japan and South Korea) so that they would not be fake leaders.

These markets produced actually competitive businesses that thrived and outcompeted the market leaders (US and European companies) in multiple industries. So if you keep tariffs forever you end up with Russia or some other backwater where people are forced to buy shitty goods because you have no access to external markets.

The computer market in Brazil, for instance, was like that. Most of what we had were pirated hardware, because there was never an effort to create a real industry in the country, they would just copy and paste whatever was available out there and "launch" in the local market, so even with years of tariffs and protectionism the country did not produce any player in the computer manufacturing market.

See the Soviet and East German automobile industries, and to a large extent the British one pre-European accession. Hideously outdated and uncompetitive, years behind the rest of the world, and both vanished practically completely when the protectionist systems which kept them alive collapsed. When the government more or less makes people buy your shit no matter how bad it is, on the basis that it is the only option that isn't taxed into oblivion, there is little incentive to make it good, and in practice this does seem to hold up to a large extent even when there are a few local competitors.

This isn't 'wrong' but only accounts for a two party market.

That's interesting, so, prices might not drop to pre-tariff levels, until not just one, but many, manufacturers appear in the US, and start competing on price (well, obviously, I guess some would say)

The economic answer is 'it depends'.