Several networks in the US still use CDMA. Verizon (which claims to have the best coverage), and Sprint (who claim their network coverage is only 1% less than Verizon).
I had a Star Tac in the UK many moons ago. Apart from novelty value, I'm wondering why the OP would want to use it?
Track usage, upgrade and get support with the My O2 appDownload My O2