Hi Moosey,
You are getting confused with a 'Wi-fi' signal and the internet 'connection speeds as advertised by a ISP'
A 'Wi-fi' signal in the most part for consumers will refer to the wireless signal broadcast by a Wifi Router. This will take in the Internet connection from your phone line and then any wireless devices you have - laptop, printer, PDA, PSP, Digi Camera etc etc can connect to it. Routers will be of various types, the older 'B' signal is now not really used anymore. The G signal and the latest N signal are the ones you'll see on the products. G is more widely known and used, the N signal is currently the fastest 'theoretical' with claimed connections of '100+ MB/sec' - in reality and everyday use, these will at best reach 25MB/sec for throughput.
If a 'Flat' is advertising 50+MB/sec broadband connection, I'd think they're referring to the ISP connection it has via BT or Virgin cable. Again, claimed internet connection speeds are nothing like reality connection speeds, I'd estimate a 50MB/sec advertised connection will at best provide between 20-30MB/sec.
Overall though, broadband 'speeds' are similar with the USA for domestic usage, I do find however, the USA is just a little more expensive for like for like BB connection speeds. However, it's usually becuase most ISP's in the US bundle services with voice telephone lines and TV services. Also, I haven't looked in any real depth at the various US options. Also, some areasof the US offer some really 'fast' connection speeds as compared to the UK. As per usual, it all depends really on how much you are really willing to pay!
Cheers, DtM! West London & Slough UK!