Maybe the difference in figures between countries
might be down to how much they can sting each government making the request. There was a recent story on how M$oft make a minimum of $200 and often $400 or more on responding to many requests. European governments tend to be more stingy in paying for information they think should be available to law enforcement for free.
The only reason the US figure is not 100% is that if it was, it would show how much they enjoy selling your private info.