I think the possibility of a large black cat existing in the States is small. But there's a chance. There's also the chance of mis-identification. And there's a chance it's a species we haven't documented yet or thought was extinct.

There were no breeding populations of jaguars in the U.S., until they found them. And Ca fish and game says there are no wolves in Ca. But I've seen them. And there are pics of them. They also say there are no brown bears here. Yet they couldn't explain the pics of two of them. Of course, they also failed to recognize their "failed" program to re-introduce both brown bears and wolves.