1. The US is by far the one requesting the most data. I'd have to run the numbers to be sure, but it looks like even controlling for population and number of FB users, the US is definitely outpacing other countries' data requests.
2. The US is the only country where FB is reporting in ranges instead of precise numbers. There could be several reasons for this, but the reason almost certainly is not that they don't know the precise numbers. NSLs seem like a safe bet here.
3. The US also has one of the highest "success" rates of government requests. 79% of government requests yield some data. This again could be interpreted several ways, but the two most enticing ones are that the US isn't sending a lot of fishing requests because when they request data from FB, they're already pretty certain about what they're looking to find. The more disturbing concern would be if the US only queries FB for things where the NSA's database is insufficient, which would mean the number of requests they submit to Facebook is not at all indicative of how many queries on user data they actually do.
EDIT: Here's a quick Gist I made of this report as a CSV. https://gist.github.com/Cowen/adb2d335862a95870773