This country, alone, is based upon all our cultural differences; it's like a big melting pot. People travel all over the world to enjoy the different ways of doing things. To have a uniform world would be to strip all of that away. You wouldn't be able to enjoy anything anymore. It would be like the whole world went black and white because it would be so dull. Everyone would be doing the same things all the time and everything would become so predictable. There would be no more expressing ourselves because someone else would already be expressing the same thing. There would be nothing left to experience because everywhere you went you would see the same things.
If everyone wore the same clothes, listened to the same music and did everything else the same, we would be like puppets to these big corporations who created the clothes and the music and the movies. They would be telling us what to like and how to like it and we would never think for ourselves.
But, if we wanted to look at it in another way, there could be advantages to having everyone the same. Everyone would be the same therefore everyone would be equal. If everyone was wearing the same kinds of clothes no one could make fun of you for wearing those clothes. If everyone was listening to the same kind of music no one could laugh about what music you listen to.
We would have a uniform world. Everything would be organized. It seems like it would kind of be like a school with uniforms. Schools have uniforms so that nobody feels higher or lesser than anyone else and can concentrate more without having to worry about what they are wearing. Having a uniform world might help make it a peaceful world. .