Why does suzuki think people should “act as one single world”? we all have different governments. borders separate our countries. there are five billion people on earth. we all live on the same planet.

Explanation:

There are over 7 billion people currently living here on earth.

He is objecting to nationalism which breeds a kind of contempt for those around your country, who do not share your government and likely not your culture either.

Think how much better if we respected one another no matter what our country of origin. Think how well off we'd be if we didn't think there was something wrong with someone just because their skin color is different.

Think how good it would be if we did not fight costly ruinous (often stupidly motivated) wars.  

That is what Suzuki wanted.

He wanted a planet we could live in harmony with, not one that we are on our way to destroying.