Tribalism is based on empathy towards other tribe members. Capitalism, ironically, goes against this: tribal bonds take a back seat to economic interest.
Humans are, in fact naturally empathetic. It's why we pack-bond with anything with a name.
It's not a matter of expanding it. Humans developed to have tribes of 2-300 people, and as a species we haven't done well past that. Look how society started turning to shit once we could communicate globally with millions of people.
We didn't learn to love and accept everyone, we just formed echo chambers (tribes) and turned the dial up on the hate.
What you're looking for is something like globalism, which goes against human nature.
Dunbar's number is 150, I believe. But that's the limit for ""real"" people, with names and addresses and birthdays. The magic is, however, they don't need to all be real: a nation is a tribe, and nations can hold millions. You just need a few real people that you take as a stand in for all the others, and then keep doing it untill it encompasses the whole of humanity.
I say "just", it's not like it's that easy, but it's doable.