Regulation was the key difference. The EU mandated a common wireless standard (GSM) to be in use across all countries. The US let the market decide and ended up

Regulation was the key difference. The EU mandated a common wireless standard (GSM) to be in use across all countries. The US let the market decide and ended up building 4-5 largely incompatible semi-nationwide networks. Thankfully time, technology, and consolidation has now reduced that down to 2 (CDMA/LTE - Verizon, Sprint, GSM/LTE, AT&T, T-Mobile). LTE will eventually consolidate that down to 1.