Is this basically an American culture?

We had a discussion the other day with my siblings and my family relatives (who have studied abroad in the USA and in Europe) Three of them studied in Europe, and four of them in the USA. The ones who studied in America didn’t face any difficulty socially, as they said Americans are very very very open to making friends quickly and don’t usually have an ego about it.

Whereas the ones who studied in Europe said it was difficult to build a social circle because Europeans are not as easy to approach or connect with at first. They mentioned that many locals prefer to stay within their own social groups and don’t usually mix with foreigners right away. So, my question is where did the Americans get this from? Is this basically a culture?