ignoring the implausability, you are forgetting England is part of the United Kingdom (total population 64 million), so in reality the UK would become 4 states, Northern Ireland, Scotland, Wales and England
England is by far the larger with about 53 million people, this would make it one of the largest states, but there is no clear line inside England to divide it, no one would be able to agree, there is no logical way of doing it
There are also 14 overseas UK territories which could be easily absorbed into US territory status, like Puerto Rico
Moving this to ASB in 3...2...1...
The problem is a state has to have a decent size as well as have local support for its existence, you cant create a state which no locals like, the only county that achieves this is Yorkshire, and apart from Yorkshire and tiny Cornwall no counties really have strong ties and identities and most of them are too tiny for statehood, so you have merger problems again
An alternative is to recreate the Heptarchy but that raises problems like cornwall and cumbria which were outside the saxon kingdoms but are part of England, and then you have Kent which was an important kingdom but is now to small for a state, and then you have the problem of London which is a fifth of the English population
EDIT: Have you heard of the US expansionist party? they have already planned this: http://expansionistparty.tripod.com/Britbounds.html
I wasn't being too serious about plausibility here. All of England would be too large in population to become one state. In my main idea of the other territories the other British constitute countries gained independence. I do, however agree that there isn't a logical way of doing it that I was aware of. So far my only idea has been to merge England's counties into states.