I've been told (through this thread) that US airports that don't have Global Entry will allow GE holders to the front of the Customs line.

Truthfully, I've not cleared US Customs at a non-GE US airport since I got NEXUS (I was in Denver last Saturday but we precleared at YVR; last year we flew directly from YQR so cleared US Customs at DEN).

Scroll back a few pages in this thread and the relevant entries should be there. I specifically asked about it and was told that it's available.

Most of the transcon flights are going to be flying into GE airports, mind. DEN is an odd case because it has heavy volume (60M passengers) but very few international flights. Most of the international flights are really transborder flights, a good number of which are from non-precleared Canadian airports.