The iDEN networks have always been considered as odd on this side of the Atlantic. This network technology designed by Motorola in the early 90s is still used by two US operators : Sprint Nextel and SouthernLINC Wireless.
iDEN is now approaching its death. FCC just allowed Sprint to use 3G and 4G technologies in iDEN spectrum (800MHz). The key feature of the iDEN technology was Push To Talk that GSM networks were able to mimic with GPRS P2T applications in the early 2000s.
With the end of iDEN and the US adoption of 3G and LTE it is the end of an American uniqueness. Wireless technological standards are now global.