I just checked "Yellow Pages" for Arizona. Kingdom Hall listings ( It didn't show double entries for multiple congs.). Showed 142 Kingdom Halls and one Assembly Hall. According to jw.org there's about 200 congs. in Arizona (for English & Spanish - about (very approximately), 10 or more for 'small' group congs. of other langs.) So that would be about 1.4 congs. per KH.
I checked all other U.S. states, through "Yellow Pages" and got 8,255 listings of KHs. I think could be close. That would put 1.7 congs per KH.