What cell phone technology is the most popular in the united states?
I'm guessing by "technology" you mean carrier. There is no best mobile carrier, Verizon has the widest 4G coverage, and is directed towards people who travel a lot or live in rural areas, while T-Mobile has great coverage in high population density areas and Sprint is the cheapest. AT&t can be packaged with cable and WiFi as well as mobile internet. All of these carriers fill a certain niche in the consumer market so you can't definitively say that one is better than the other.
As a Canadian I'm not qualified to answer this. I can only presume that cell phone technology has evolved the same in the US as it has in the rest of the industrialized world. The carriers have the technology in place to support a 4G LTE network allowing for fast enough data transfers. Apparently T-Mobile has the best data rates