The IPv6 Transition

If the US had the same IPv4 scarcity as the rest of the world (specifically, if major US ISPs were using CGNAT), the IPv6 transition would be happening much faster.

The addresses were allocated equally geographically, and then sold. The US will hit ipv4 scarcity when the US stops being the richest country.

That's probably true for consumers. For large, global corporations, IPv6 is a million miles away. I've worked with several, and they all have poorly managed kit, vulnerabilities everywhere, poor documentation/diagrams, poor performance, millions of firewall rules, tons of vendors to connect with, outsourced wireless vendors, remote access solutions that are a byzantine security mess, ... IPv6 is suicidal for most large organizations beyond ok we can speak IPv6 for a small part of the infrastructure. Add to this the recent deluge of VPNs everywhere (probably due to WireGuard) and container networking, IPv6 would be a recipe for disaster. Security is difficult in this scenario, in part due to the people implementing this stuff don't have a good handle on what they are doing.

Prior to the establishment of the RIRs (Regional Internet Registries) the IANA handled IPv4 allocations directly and without regard for geography. During that time most of the early adopters with US government, US Universities, and US Corporations. Several US Universities and Corporations (for easy examples, GE and MIT) simply asked early enough for IP addresses and got entire /8 allocations.

Sure, when the RIRs were built they were assigned roughly equal shares of the remainder of IPv4 space, but it certainly failed to account for those early years of early adopter allocations, which did accidentally favor the US heavily.