I agree, I know a lot of Americans and they are are just people, all different. I think there is a cultural trait in the US to say how fantastic, super, faboulous, amazing and awesome things are, even if they are fairly mundane. The superlatives can be quite confusing at first, until you decode what people really like, versus what they are just being polite about.
Im English and we can tend to be sardonic, positivity from us sounds like 'Whats the worst that can happen?', its not a better approach than in the US, its just cultural.