Technically, TSA is understaffed at some locations based upon throughput and equipment requirements. On the other hand, some locations are overstaffed based upon throughput and equipment requirements.
An interesting correlation that I have noticed is that most medium or smaller airports run in streaks. So, at some airports** from 0430-0700 everything is running wide open, then from 0700-1000 it is small pushes here and there, then from 1000-1200 it runs like a faucet. So, if you come at 0630, you can wind up in line for a while. If you show up at 0900, you can walk right up and go in and be done in 5 minutes or less. There may be a perception that there are a lot of overstaffing situations, but I can tell you that is probably just appearances for the most part.
** Times are completely made up and not reflective of any specific airport**