I hate necros, but since everyone is discussing the relative strengths and weaknesses of American and British federalism, I feel the need to interject.
Really, the reasons why federalism is breaking down in the US are that:
1. American politicians are power-mad lunatics. Seriously, there must be something in the water here...
2. Control of a state government is the perfect way to combat the ultimate evil (i.e. the other party) at all levels of American government.
3. The state borders have not, in many cases, changed in 200+ years. Even Britain has had the sense to update it's political subdivisions more often than that! If America were to start from scratch today, the state map would be unrecognizable.
Aside from that, American federalism is probably the single most effective feature of our government, and probably has headed off way more civil wars than it has caused...
I am confident that our more erudite and circumspect British cousins can avoid these pitfalls though.