I worked at a Ford dealership years ago in the US. I don't remember all the specific details, but there were a few denied warranty claims because the vehicles were not originally sold in the U.S. but were currently in the U.S. seeking warranty repairs. I believe they were vehicles from either Mexico or Canada. The other times when warranty claims were denied was because of abuse and/or unapproved modifications which were clearly specified in the factory warranty manual provided with every new vehicle. (Please let's not start a discussion about the Magnuson-Moss Warranty Act)
Chum lee