While I don't think Japan should be judged solely on its fax machines (they're ahead in some places and behind in others), there is a difference with fax machine usage in Japan vs the US - they're a trailing indicator of another bottleneck. Fax machines are so widespread in Japan largely because they ease the process of physically stamping documents with a registered stamp (a hanko), which is used instead of a signature. So far they've failed to digitize them, and it's often cited as a huge cause of bureaucratic slowdown, especially in the pandemic. One of the goals of the new prime minister is to finally start phasing them out.