Well, you seem to be confusing a war with a battle, or in this case just a skirmish. Has the US lost battles or skirmishes in the time period the OP was questioning? Absolutely we have. Hell, I’d say we lost the Vietnam war, even though we won many of the battles. We didn’t achieve our strategic objectives, such as they were (i.e. there isn’t any South Vietnamese government today), so I’d say that’s a loss by any measure. I can’t think of any other ‘war’ in that time period we out and out lost, however, though, as noted, we did lose battles in that time period for sure.
Like I said, I figure you were being hyperbolic and exaggerating for effect. It’s sensational to say we almost lost in Grenada, considering the disparity in forces, but we really never had any chance to lose in the conventional sense. We might have chosen not to continue, and certainly we could have lost a tactical battle or skirmish, especially as much of a cluster fuck the planning was for the operation.