A lot have disappeared due to automation, and even if you place trade barriers that raise prices for Americans, the end result is likely going to be a lot more automation and few good paying manufacturing jobs.
The time where it is cost effective to pay high wages to low skilled labor is past. It's still practical to use cheap foreign labor if it is cheap enough, but it's cheaper to automate than to pay line workers middle class and upper middle class wages.
The Democrats are very good at exploiting those that don't want to accept reality. They're good at lying to people saying their problems are all someone else's fault and that you need to vote for them so they can fix those problems.
The Democrats have no solutions to the loss of manufacturing jobs other than try and force companies to do things inefficiently to give jobs to people, which is what the unions have been trying to do.
Our corporate tax rate is the second highest in the industrialized world. If you want some of those jobs to come back, then lobby congress to lower the tax rate to something more human, like 10% (instead of 35%).