Yeah, this is the problem. If you're on an immigrant visa, working a real job, then you have a life in the US: an apartment or a house, a pile of belongings, maybe a spouse and kids. If you need to leave the country to renew your immigrant visa, you may not be allowed back in to pack your apartment, sell your house, or help your US spouse and kids prepare to move to a country that will allow your family to stay together. It's a giant neon sign telling you you're not at all welcome here.
Of course, if you have a spouse and kids, this all gets easier once you have permanent resident status. Which used to be comparatively easy to get once you were married and you had offspring running around. I don't know what that process looks like now.
In practice, this kind of arbitrary screwing with people makes the US far too risky for educated, professional immigrants. So the scientists and the engineers and the company founders will just go elsewhere and build that country's economy. Which is fine, in the long run: If the US doesn't want to build the future or create new industries, then the voters have every right to vote for that. We've already decided we have no hope of competing with China in cars. And we'll need to cede more industries over time. As far as I can tell, the US has benefited heavily from poaching other people's scientists and engineers and professionals for decades now. But maybe the voters don't buy my argument, and they believe that chasing away skilled professionals and imposing 100% tariffs will lead to the future they want. It's a difference in beliefs about about what makes a country prosperous, and people have a right to vote based on their beliefs.