By Nora Eckert DETROIT (Reuters) -Automotive executives are bracing for a freefall in U.S. electric-vehicle sales following the disappearance of a critical $7,500 tax break for buyers. "It's a game-changer," Ford CEO Jim Farley said during a Detroit event on Tuesday, just hours before the federal subsidy expired. Farley said he would not be surprised if electric-car sales drop to 5% of total U.S. vehicle sales next month. That would be about half the level from August – a monthly record as consumers hur ...