The US has no infrastructure to make up for the lost imports. That means that 1) they import at a higher cost and pass it on to us as inflation, 2) import less driving up demand and therefore we get inflation, or 3) one of those options plus billions of dollars to create a factory, and the we get even more inflation as the factory costs get passed on to us as well.
There is no option that does not drive up prices.
Sure. After all, the reason there were imports in the first place was reduced production costs. Stopping imports, especially suddenly, can't be without effects on consumer prices.