What's actually wrong with the concept of one world order?

Whats actually wrong with the concept of one world order?

Wouldn't it be better for all of us on this godforsaken planet if everyone just got along, and didn't care about silly, trivial issues like nationality? A world without passports, artificial lines in the sand that exist only in the minds of people, and the constant bickering (i. e. wars) that flare up because one group of religious zealots believes that their god is better than yours, or you have something in your territory that he wants (like oil or gold).

We have only one planet, therefore it makes perfect sense we have only one government, one currency, one language and one "nation". It's time for the human race to finally grow up and ditch all these ridiculous tribes.

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Not one person thus far has given me a single good reason to oppose the idea of a centralised, worldwide "nation". All I see are the cliched, and highly emotive, dismissals of the idea that I usually come across from people who clearly haven't given this idea much thought, but who have nevertheless been exposed to a lot of asinine propaganda from those invested in the current, chaotic system, a system that is clearly dysfunctional and on the point of collapse.
What's actually wrong with the concept of one world order?
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