Well, the only way that would happen is if we encounter another sentient species from another planet, that doesn't like us very well. So If the earth would be unified, then that means we would be fighting aliens.
What if Earth was a 1 nation with 1 race and relig: 2015-11-30 16:33:40
Humans are already one 'race'. That is, actually, there are no such things as actual biological 'races' of humans. What we typically call a 'race' today in everyday language is far more cultural than biological. Superficial appearances, such as skin colour and facial features are but a tiny tiny fraction of humanity's genetic diversity. Most of our genetic diversity is not noticeable by looking at a person; examples are differences in peoples' immune systems and other internal organ functioning. We are already far more related to each other than we are different from each other.
So, I'll ask a more daring question: What if the Earth had no nations, no concept of 'race', and no religion? I think it would be much better than an Earth with one nation, one imaginary 'race', and one imaginary religion. (Though I'm open to debating the 'one nation' thing.)
What if Earth was a 1 nation with 1 race and relig: 2015-12-01 07:52:19
If everyone wanted to be in one country together (far from that today), then there would be no more war, and things in general would be much much better, but eventually, the confederation's lands could become countries again.
What if Earth was a 1 nation with 1 race and relig: 2015-12-02 03:43:03
"Look, this baby in Nazareth has a cool new idea about how we should behave!"
"Fuck you! I'll kill you!"
*Everyone's back at fighting*.
It wouldn't stay that way for long.
Fundamentally, we would either be all brain-washed or it'd be forced. Humans like to dislike. I dislike people that say that shooting people is OK. I enjoy disliking them. We don't just dislike important things, but ones of no consequence. I dislike the new Fiat 124. I dislike this website's colour palate. This inherent disliking leads to fights, and people walking off, fighting off, and making their own countries.
What if Earth was a 1 nation with 1 race and relig: 2015-12-02 14:01:26