Could humans be one?

What is stopping the current global status quo from democratically coming together to set international agreements and focusing on global prosperity while still preserving national strengths and individuality?

Couldn't the world leaders somehow create joint operations where every country in the world has a representative, that could convene to discuss and solve global problems together while making sure the agreements are held.

A global meeting ground where race, religion and nationality MUST be set aside in the name of Humanity.

When I think of humans as animals, which we sorta are, every conflict imaginable between countries and people seems really dumb in the way of evolution