I know on my Jensen, when off, all I've got is the AM/PM indicator and the time digits. May be a different model, but, I wouldn't expect the USB indicator to be on unless a USB device were attached...
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)