I would have to say that the US would probably fare much much worse in a similar way to the UK to the Japanese scale disaster . Infrastructure throughout the USA is quite poor as in the UK and has been designed not for resilience but the lowest common denominator of the lowest cost basis. Throw into the equation God, guns, race and politics and an equivalent disaster would be an exceptionally bad day for the UK and USA (although we don't have to worry to much about the God and guns part of the equation over here in the UK just as in Japan. )

Even the US military would be poorly equipped on the command psychological level to quickly put together a response plan despite the physical assets they have access to. The ability at the bottom of the command structure to formulate, adapt and carry out their own response plan I suspect would be quite poor. The UK military (known as the borrowers) don't have access to the same resources as the US military but we do have Staff and Sergeant Majors to keep the Officers on the right track.

Civil management of the response plan would probably be quite pitiful for both the US and the UK as well. Too many chiefs and not enough Indians with the Indians asking the Chiefs 'What the hell are you talking about' because the Chiefs basically have a poor technical or engineering background having graduated from University with a Harvard Business Management or Oxford PPE degree.

Having a UK Prime Minister (educated in PPE from Oxford University ) in the UK taking charge of a Nuclear Reactor emergency would fill me with absolute dread. For some reason the Japanese don't seem to have a problem though as the Japanese Prime Minister dons his boiler suit.

I guess we all know this - This is why we prepare (just in case)