Black Cats

The other day I was returning from a ride and a beautiful black cat ran across my front tire.  He, or of course it could have been a she, narrowly missed being hit.  It was a lovely creature, but was it unlucky?

You see, back in England black cats have always been considered lucky.  I well remember that in my youth, married couples used to arrange to have one let free in front of them as they left the church.  However out here, the reverse is true.
Now as an ex-Englishman living here, do I bring the English custom with me or do I accept the American version of luck and why do they vary.  Does anyone know?