We yearn for answers to why we're here, there's a reason religion has been such a huge part of there human consciousness for so long, our brains are hard wired to find reasons for everything.
Since there is no known objective answer to this question, I'll answer it subjectively, recognizing that my life experiences have tainted my views.
Life has no purpose. People who do immense "evil" will not be punished. People who do immense "good" will not be rewarded.
Your existence is a beautiful, flighty phenomenon. You are a heap of octillions of atoms that somehow gained self awareness. Your happiness is merely a chemical exchange in your skull meat, it's fine to strive for happiness but it's fleeting.
I personally strive for serenity, accepting reality for what it is and making peace with it. Nothing matters, we're all going to lose the gift of consciousness through inevitable death, and that's okay.
Globalization is already well underway, our economies are entertwined, our technological advances, our medicine, knowledge, and even entertainment.
There is war, incompatible theologies, racism, hate, and all sorts of stuff that has the appearance of not being "united". As long as humans exist those things will persist. We're not robots, our flaws exist because of the nature of our biology.
I think it's fair from at least this perspective to say we're already united.