Really? The US effectively excluded 70% of the population (the poor, women, non-whites) and from effective political participation until 1920 or so. While you did have that nasty civil war over slavery, I'm not sure that the history of the United States between 1776 and 1920 could be described as a "disaster."

China has effectively excluded 95% of the population from political participation since 1949, and has been stunningly successful over the past 20 years.
These seem to me to be exceptionally apples and oranges comparisons.

It's easy to oppress a minority and keep the lid on things, for a long time at that. Different with majorities, whether they be the poor, or a different sect.

And I think we (US) had a civil war in the 60's and 70's as well, but it just didn't bubble up to the level of conflict that we would identify as a civil war from traditional perspectives. It was also localized to geographic areas. My parents never felt quite the effects that Blacks in the deep South did.

China's a rather homogeneous state, and could probably be stratified mostly by the classic Marxist means of looking at the problem from a proletariat and bourgeois perspective. I haven't touched those old Communism in modernity texts in a long time though, so the analysis there could be off.

I would say, however, that the cases you mentioned are outliers because of these facts.