Someone out there may have written a report, but if not, you could do this with the native search tool. (Not the one built into Explorer.) If you are logged in as someone with access to all folders and all states....
It will tell you how many files you have found, then if you want to do more with the results (i.e. filter via extension) export it to Excel where you can data mine to your heart's content. (or you could run the search tool several times with different file extension filters.)
If you need this information often, a report would be worth writing, but just a once-in-a-life-time thing, the Search tool rocks.
Jeff, thanks, I will try that.