Earlier quoted context omitted.
Americans tend to have larger, more casual social circles, probably. Having hosted parties in both the U.S. and Europe, the "flake rate" in Europe is much smaller, but the parties are also smaller, less frequent, and planned further ahead of time.
"Europe"? I can assure you, the party cultures in Spain, Scandinavia, France and Greece are all pairwise so dramatically different that the U.S. are not the counterpole, but just another flavor in the sea of possibilities. The same applies to different cultures within these countries. Across areas, ages, socioeconomic backgrounds, political leanings, hobby groups. It's astonishing to me how many comments around here…
Fair point, I didn't mention where in Europe I live. (The German-speaking part which is maybe the part I'm generalizing about).