R&S: Why are so many people oppose a one-world government?

One currency, one language, one culture, one unit. We would all be united, and all cultures will be dismantled in favor of western culture which is proven to be the most enlightened, one language which will be English, and one currency. We will all be united, and we will have worldwide schooling and promote education and the sciences. Why do so many people oppose this? Surely, this is the only way forward. It's like how famous scientist Michio Kaku said, the only way to achieve a type 1 civilization on earth is to become united in culture and language, as then we will all have an incentive to share and advance our species.