As the factories come back so will unionization which will help.
I wouldn't make the assumption that there will be increased unionization. There could be, but I wouldn't assume that it's inevitable. Companies will still want high productivity, which will mean they will find ways to keep the head count right where they want it. Re-shoring isn't necessarily a jobs program - at least not across the board. For some industries, absolutely, but the pros/cons won't be uniform.
We kind of saw during Biden's term how the assumption of a jobs boom simply by bringing production back here doesn't necessarily pan out as predicted. Biden wanted to use policy as a cudgel to force foreign tech companies to make their stuff here. Turns out, they want to bring their workers, they want to do things their way, not ours. We've also seen how Elon and Vivek were really pushing hard to keep the door open for H1-B visa holders, basically allowing for more imported labor, which I think isn't how Lighthizer sees this industrial revival shaping up.
There are other valid reasons to reshore, though. In 2017, Hurricane Maria took out saline production in Puerto Rico, which just happens to be a nerve center in the global saline supply chain. Saline is critical for its healthcare applications. A few years later, we saw how a lot of our medical supplies were manufactured overseas and many of those countries wanted to prioritize their own domestic concerns first, which is certainly understandable but also underscores the need to produce at home. Ditto things like our ship-building industry, which pales in comparison to China's.
I voted against Trump all three times he's run, but he's not necessarily wrong on this one. I wish it had been Obama who had first proposed it, and I wish Clinton had made it part of her campaign instead of running ads of wind turbines in Southwestern Pennsylvania and West Virginia. Democrats used to run on this brand of economics. They've run away from it since the 90s, and it's kicking them in the ass.