The first successful MVNO in the US came only 3 years after the first successful MVNO in the UK and mobile number portability was put into law in 2003 for both the US and the UK. The additional benefit is that because mobile numbers and wired numbers share the same area code base in the US, US number portability is basically universal. I don't see the basis based upon your listed criteria for saying that the FCC cares any less or that Ofcom cares any more about promoting competition.