However (and at risk of sounding hostile), can I ask what other cultures have you experienced?
All cultures have good and bad things, it’s not xenophobic or racist (I hope) that the Chinese have statistically better school conduct and order, while the Russians are impressively tough, the Spanish are very chill and relaxed, and many more examples.
As with all previous examples, Americans have many such qualities, but I wouldn’t have thought to say polite as one of them. Maybe for the Japanese. Hope it doesn’t offend anyone. At least around here Americans have more a fame of being loud-ish and sometimes a bit lacking in reading the room. It’s absolutely terrible but, have you watched Emily in Paris? Kind of like that.
I however understand you considering Americans polite if your other comparison is, for example, Egypt.
Just so it doesn’t offend anyone, here’s some qualities I associate with Americans. Creative, resourceful, fighters for freedom and their own personal rights (litigious too), despite the current political climate.