If our fighter jocks couldn't tell the silhouette of American equipment from 500M, I'm not sure how they would see an 8 inch star on gas tank of a moving motorcycle on the inside of some guy's legs!
On the other side of things, the "invasion stripes" put on planes at Normandy was a result of getting our planes getting blasted by ground troops in Sicily and other places by GI's nervous about LuftWaffe attacks.
(Un)friendly fire, I'm afraid can go both ways. Now-a-days there isn't much confusion from the ground to air side as anywhere we fought in recent years we have had air supremecy. Air to ground side, however, I am sad to say there are still incidents. How you can mistake a Marine AAVP7 for anything other than a Marine AAVP7 is beyond me. Here are some info about the AAVP7. On a side note, the Army's new Styker vehicle looks a lot like a BTR and the new Marine AAAV (Advanced Amphibious Vehicle - not yet fielded) bears an unfortunate resemblance to a BMP.
Stryker
BTR
AAAV
BMP