Well depends on your metric. China is a successful communist country if you look at the fact they once called themselves communist and that they are a super power now. They are not a successful communist country in that they they are a hostile country with concentration camps

The USA is a successful democracy in that it calls itself a democracy, and is a superpower. It is an unsuccessful democracy in that it has routinely assassinated democratically elected leaders in foreign countries and on its own soil has far too many people questioning its own democratic system's integrity

South America had no communist countries (I may be wrong), but had plenty of successful socialist countries, but these countries we in turn unsuccessful, because they couldn't fight off foreign powers from replacing its leaders with brutal dictators

Now people love to point at mao and stalin and play the gotcha game, and they're not entirely wrong. They tend to forget the times when the states or brittain installed a right wing dictator in a foreign democratic country for capitalist reasons. Certainly saddam hussain wasn't a pinko commie, and he was pals with the US (until he wasnt)

Anyway, im sure that I'll get some hateful comments, and that's fine. People that legitimately think that with Bernie or AOC in charge (hypothetically) that the next step is forced labor on collective farms are basically as dumb as a fencepost