I just adopted an American Bulldog. I have a housecat and have been advised to leave one or the other. Is it true that bulldogs and cat's don't get along?

Hello! I just recently adopted a 3 year old American Bulldog. She has never been around cats so introducing her to my cat Bob has made me nervous. I was reading about American Bulldogs and it says that they don't get along with cats unless they have been around cats and my friends are telling me to get rid of the cat or give the dog back. I just don't believe that because of a dogs breed they couldn't get along with a cat. I did read the article about introducing dogs and cats and so far I have been doing everything correctly. Brix (the dog) will stay when I tell her to and just watch Bob (cat). I do not take her leash off and I've been putting the cat in one room for a little while and then putting Brix in a room and letting Bob out. Bob does creep up to her but I tell her to stay cause the second she moves he poofs up and growls at her but she never growls back or barks (still havnt heard her bark yet!) and she shakes a lot. I guess my question is: Is there any truth to American Bulldogs not getting along with cats if they havnt been around them?

Thanks so much!

Destinee