GAI and fusion are different issues in that we have clear elementary understand of fusion (and a large chunk of the technology worked out). We have little to no understanding of cognition and much of the technology that we use for AI now may (or may not) prove to be irrelevant to GAI.
I'll challenge that, because I think tribalism (living in small groups) is the way more akin to our genes. And much from the rising mental problems of humans today comes from living on your own in a big anonymous pool of strangers.
But those small groups could then indeed work (more) together for the common good.
But .. actually there is also enough space on earth left ... poplated areas are very dense compared to big open lands.
Why?
I didn't say we should live stone age style. And using technology is very akin to our genes, afaik. So I don't see any problems with that. What matters more than the tools are the social interactions I believe. And there we could do better.
In short, I'd like humans to just get on with each other and treat the world we share with other species with greater respect. If that puts me in a tribe, then so be it!