Taiwanese and Korean voters (and voters in a lot of other parts of Asia and Europe) believe that providing high-quality infrastructure and public transit is a basic duty of government. If the transit situation got bad there, the politicians would be worried about losing the next election, so they don't let things get bad.

American voters just have lower standards. This is true in a lot of other areas, especially education. If American politicians believed they would lose re-election because of bad infrastructure, the money and commitment necessary to fix the problem would suddenly, magically appear.

Are they dealing with the same climate issues? The extreme hot/cold cycles really tear up Boston’s roads.

Korea definitely experiences temperature swings. For example, the average highs for Seoul[0] are very similar to the average highs of Boston[1].

0. https://en.wikipedia.org/wiki/Seoul#Climate

1. https://en.wikipedia.org/wiki/Boston#Climate

Parts of Japan's climate are in many ways like New England's climate, though Japan has more subtropical regions obviously, and also more mountains.

Both get plenty of snow and get humid in summers.

Korea has even more extreme hot/cold cycles. Even Taiwan, in the mountains, gets cold/snowy in the Winter, and what I saw there was that there were zero roads as bad as in, and around, Boston.

Also, in Hokkaido I never saw such bad roads, either.