They also lead because they are number one in economy (Wallstreet), culture (Hollywood) and politics (oldest democracy alive).
I do not believe this statement is entirely true. In terms of economy, the US is the top dog in the world (unless you count the European Union).

But why is America is number one in culture? Because it can afford to spend the most on movies, which though visually spectacular, are shallow and for the most part badly acted. What about other forms of culture such as cuisine, theatre, arts, architecture, literature...? Bollywood produces far more films than Hollywood does.

Iceland is an older democracy than America and possibly the world's most pure democracy.