It's probably more due to increased asymmetric partisan polarization than anything. The same issue shows in polling on the economy. When Trump was in, republicans reported that the economy was great. As soon as Biden took office, the economy was doing horribly.
If one of them gets into power, Canada might just pay for that wall.
I get the reflexive urge to both-sides things, but rail workers did end up getting their sick leave:
https://www.reuters.com/world/us/most-unionized-us-rail-workers-now-have-new-sick-leave-2023-06-05/
https://www.theguardian.com/business/2023/may/01/railroad-workers-union-win-sick-leave
Biden wanted to avoid the disruption that a rail strike would bring, especially when we were trying to deal with inflation, but like many things, they quietly got it done.
Smart cars had to pass US crash test standards and have the appropriate safety equipment. The kei trucks that you can currently import and use are 25+ years old and wouldn't have even passed US standards back then. Your legs are the crumple zone in these things.
I assume that new ones would have a chance, but it'd be expensive for a manufacturer to modify and certify for the US market. Small cars haven't sold well here, and the profit margins are slim.
Maybe with the recent size and price increases in autos here, well see some movement. I'd love a modern Honda kei to go with my element.