I don't doubt the horrible things many of you mention in America, but must say I have no experience of any of them.
I/we moved from London to a thriving 'secondary' city in America.
What I like about America:
Physical space - large yards/gardens, good sized houses at affordable prices (my 4 bed house here costs the same as my 2 bed London flat).
Transportation - I like the ease and convenience of a car. Yes, i miss walking in a city and would like the option of public transport (which is largely non-existent where we are). But I don't miss going out in the pouring rain to walk to/from school, waiting at a bus stop in the bad weather for infrequent/too crowded buses, trudging around with heavy shopping bags, etc.
Healthy Lifestyle - while I think Americans can be too puritanical about drinking alcohol (friends here 'allow' themselves 2 glasses of wine on a 'big' night out), the regularity of prodigious drinking in the UK is unhealthy and astonishing. Perhaps it is the weather in America that makes it possible to plan outdoor sports/activities with some certainty, but most people i know here are quite active physically.
Charitable Giving - while it is true, that there is not the same government 'safety net' here with little equivalent of council flats, Housing Authority flats, etc there is a gigantic moral imperative for those who are 'fortunate' to 'give back'. While the government might not look out for you nearly as well as in the UK, churches and private charities/foundations fill the gap admirably. Almost everyone I know did some sort of charity work (in addition to giving) this past holiday season. Whether working to raise funds for the Children's Hospital, giving toys to families on the Angel Tree so they could have gifts for Christmas, contributing food to food banks, delivering meals to those who need them, etc, almost everyone here does something for those in need. Americans give (time, money) at an astonishing rate.
What I miss about London:
Friends - as a generalisation, people in America, are very schedule driven. There doesn't seem the same easy ability to be spontaneous. i think people genuinely want to be friendly/meet up here, but actually making it happen can be tricky (hence the impression of superficiality).
Diversity - it is here, no doubt. But you have to make a concerted effort to 'find' it. Many cultures tend to 'stick together', so there are Mexican or Kurdish or Asian shopping areas and neighbourhoods. I think it is as much a function of various nationalities/cultures 'sticking together' as Americans being insular.
Culture - I miss wandering out to a world class exhibition with little/no advance planning. I feel envious that I can't go to a wonderful event at the South Bank, or see the people on the plinth in Trafalgar Square (or whatever other event is going on). There is a fabulous new symphony hall where i live, one of the best children's theatres in the country based here, a vibrant music scene, a stunning exhibit of paintings by Georgia O'keefe at the museum currently, etc but it is not the same as London.
I'm sure I'll think of (many) more, but will stop this essay for now.