We’re at 124% debt to GDP, France is 111%, England 104%. How does Japan keep their economy at 254% debt to GDP? I don’t know much about Japan’s economy.
Excellent question!
70% of that debt is actually held by the Bank of Japan - ie they monetized it. Comparatively the BoJ has done 5.5X more QE than the fed relative to overall debt / GDP.
As well, Japan has some significant advantages.
1) They were first at this experiment, which has its benefits. So they had the rest of the world to export their deflation to. Also Japanese companies built factories all over the globe, so they could make money there and send it home.
2) The Japanese culture is very homogenous. The government tells them to go work hard, and buy government debt for the good of Japan, and people do. Do you imagine that working here?

3) They have been in a period of very low growth for a long time. The median household income in Japan is like 40% less than here. Surprising for such a modern country I think.
So they muddled through for a long time. The yen recently fell to a low not seen since the 90's and inflation set in. The BoJ started raising rates which helped, but it also partially unwound the carry trade. The new Prime Minister has seemed to reverse some of this, so the yen has started to drop again. Unsure which direction from here?
China is in a similar situation to Japan in 1987. There housing market has imploded, and there population is aging / declining. There trying to reflate it. Where that goes I don't know.
Anyway, all this macro stuff is too much for my puny brain. What I do know is 2% inflation is very different than 3.5% inflation from an investing standpoint. It doesn't sound like a lot of difference until you compare it to the massive debt service required globally.
3.5% is likely much better for investors, but as
@RAVL pointed out its much harder on the working class, which leads to unrest type problems.