That means wages have equalized in every country, which is a good thing. I was talking with someone a few years ago who is from one of these third world countries who lamented that corporations were coming in. I asked them whether they thought the people who worked there would prefer a relatively stable factory job over backbreaking farm work, factory jobs which usually pay more than the average wage of the area anyway in order to entice people to start working there. Free trade is good.
Factory work is not going to come back to the west in a big way. Labor costs would make goods more expensive than customers would be willing to pay.
When there are no more humans willing to do the work for cheap, which will happen when the third world catches up with the first world, everyone (including third-world factories) will pivot to robotics and automation as much as possible.
Really not sure what trade relations between the US and China has to do with the very general strategic practice of placing factories in countries with low wages and limited worker rights, in order to cut costs.
China is not the cheapest place in terms of labour costs. Hasn't been for decades.
But my point is that contrary to the rhetorics and the politics, western countries hasn't stopped trading with China, actually the opposite has happened.