Catholocism is a continuation of the Jewish faith. The major difference is that we believe that the Messiah has come. Christ is the Messiah of prophecy, according to Catholic belief, while the Jewish religion is still waiting on the Messiah.
It isn’t the Crusades. The Crusades involved Christian people fighting wars to reclaim Holy Land and defend Christian people in the Middle East.
Since Christ was crucified, some Christians placed blame on the Jews for His death, and that may be why there is some friction. But, it’s obviously wrong to blame an entire religion for that, especially since it was His plan all along to sacrifice Himself for us. (Somebody please correct me if the following statements are incorrect!!) I believe that Vatican II stated that blame is not to be put onto the Jewish people, as a whole or the individual Jewish people that turned Jesus over to Pontius Pilate. But the Second Vatican Council wasn’t too long ago, in the grand scheme of things, so there may be some leftover hostility from the beliefs of some Christian before that.
If I may offer some advice in dealing with your Jewish friends- be polite, respectful, and loving. As Christians, we should show to everyone the love that has been shown to us. Teach others by example: live a Christian life, love God and love your neighbor, treat everybody as though they’re a piece of art created by God Himself. (Because they are!!!)
Anybody reading this- if I’ve made any errors, please correct me! As far as I know, what I’ve said is true, but I’ve been wrong before and I’d bet the farm that I’ll be wrong again!