How long ago was this? In the past couple of years, I believe the backend systems have been integrated so you can use Tokyo-specific cards in Osaka and vice versa

This March. I wasn't able to use Suica for the Osaka busses.

Were you using some minor bus company? To a first approximation, all Japanese IC cards are compatible these days.

https://en.wikipedia.org/wiki/Suica#Interoperation

Actually on second thought, this happened in Fukuoka, not Osaka. In Osaka I was able to take the metro with Suica.

I ended up carrying around cash and change anyway since a lot of places in Tokyo were still cash only.

I’ve used suica from Hokkaido to Kyuushuu. Some local bus lines don’t accept it, including the one in my city, but they seem to be gradually adding suica compatibility everywhere. It’ll probably be universal in a few more years (tech adoption is incredibly slow in Japan)

Suica is produced by JR East. In Osaka, what about the equivalent card produced by JR West?