I suspect America does well because its agenda doesn't cause it to pick pointless fights and Teddy's hidden agenda is permanently locked to Environmentalism, which he benefits from. Other civs tend to roll ridiculous hidden agendas which they can in no way handle, e.g. Populous Spain (using what mechanism to create population above everyone else?) or Cultural Scythia. It doesn't help that AIs are constantly offending each other because of "units near borders." They don't trade with each other, and even when they go to war what they mainly do is just shred each other's units without anyone winning or losing.