The badly set up computer system was in America, but the computer McKinnon was using was back here, in his bedroom. If he's committed an offence he did it here.

If the prosecuting authorities here don't think its worth prosecuting him, there is nothing to stop the Americans trying take a civil action against him here.

If McKinnon had been an American, and he was accused of hacking into MI5 or MI6 computers can anyone conceive of his being sent over here to be put on trial? Actually you can be pretty certain they'd hush the whole thing up, they'd be so embarrassed at being shown up as buffoons...