US cellular service is actually not too difficult to understand. CDMA is technologically superior to TDMA. It provides better call quality. The original GSM was based on TDMA (UMTS is, in fact, CDMA). In the US, where the government decided to let companies develop their own networks, AT&T and Verizon became the two dominant carriers (I'm ignoring a lot of the history here).
AT&T used to be TDMA (I'm guessing because it was an easy upgrade from AMPS). They then switched to GSM, but because the European frequencies were in use here, they used different frequencies. AT&T is continuing on the GSM upgrade path.
VZW deployed a technologically superior CDMA network. Since most Americans don't travel between countries all that much, it's not really a major problem. The upgrade path for CDMA was much easier than switching everyone from CDMA to GSM. So Verizon continued to use that path to EV-DO.
4G would require a massive hardware upgrade regardless of what network the carriers were using originally, so VZW is pushing LTE (the 4G GSM standard). LTE will likely use VoIP for voice calls, so within a decade, most of the US should be on the same system as Europe.
Basically, the point is that there's a good logical explanation for the network progression in the US. It doesn't help that AT&T has poor network coverage, customer service, and just about everything (except phones). VZW's obsession with locking out consumers is annoying, but most of the people who care about this can get around many of these limitations, and the rest don't care.