The US isn't far behind. The US had over 90% 4G population coverage long before it was wide-spread across Europe. Europe lagged far behind the US in fact. [1] It is expensive. You're conflating two separate things. The US had unlimited data plans longer than five years ago. Some carriers briefly went away from them and are now going back to them due to competition.

The UK has a median income that is barely comparable to the poorest US states. [2] Why would it be surprising if our goods cost more? Despite that, our cost of household goods is almost universally lower than the UK, with a few exceptions like wireless.

[1a] http://www.telegraph.co.uk/technology/mobile-phones/10288585...

[1b] https://www.wsj.com/articles/SB10001424052702304914204579396...

Feb 2017: "UK trailing behind Europe and US in 4G usage"

[1c] http://www.vanillaplus.com/2017/02/25/25474-missed-connectio...

"Europe slow to adopt 4G mobile: sector execs"

[1d] http://uk.reuters.com/article/us-telecoms-idUKTRE78Q60W20110...

Mar 2016: "Stop whining, America: Your LTE makes Europe look slow"

[1e] https://www.theregister.co.uk/2016/03/10/twin_prime_global_n...

[2] https://mises.org/blog/if-sweden-and-germany-became-us-state...