I don't know about nationwide, but here in my neck of the woods, The Great Raid was only on one screen (out of about 50 screens in the immediate area).
Perhaps that would account for the low numbers.
I wanted to see it, but the theater that was showing it is a real fleabag.....
In New York, it was on a number of screens. I caught a 10:20 showing, which was pretty empty. (3 people per row!)