Depending on the time frames in question, it easily could have been that Japan and Taiwan had massively faster internet on average. Ten years ago, a 10Mbit connection here in the US seemed to be pretty dang fast.[0] However, speeds in many metro areas in the US have massively caught up to the rest of the world. Rural areas are still often left in the cold, but in many cities its not uncommon to find 200Mbit+ residential internet connections available. And like I've mentioned elsewhere, gigabit is available in literally hundreds of towns in the US. The average AT&T internet user these days has ~99Mbit, the 90th percentile having 323Mbit.[1] I doubt that was the case even five years ago. So its not a case of Japan or Taiwan's major fiber metro areas getting destroyed, but more of the US finally getting good metro fiber deployed to more customers. Maybe the internet hasn't changed in the last decade where you're at in the US, but its very different in many other areas.

Of course this speaks nothing to the average prices these consumers pay. However, its probably a lot cheaper to wire up an area less than the size of California (Japan + Taiwan) with a much more massive population density. If everything else was equal (its not) it would have surprised me for internet to have been more expensive in Japan or Taiwan than in the US.

[0] https://transition.fcc.gov/national-broadband-plan/broadband... [1] https://broadbandnow.com/ATT-speed-test