What do Catholics believe that Protestants don't?

Catholics believe in: Apostolic Traditions & Holy Scripture

Protestants believe in: Holy Scripture

Catholics believe in: Faith is found through the Sacraments/Sacramentals (Including The Word of God)

Protestants believe in: The Word of God

Catholics believe in: The Pope is the successor of the apostle St. Peter

Protestants believe in: Sola Scriptura

Catholics believe in: Faith & Reason

Protestants believe in: Faith Alone

The difference is that the Catholics were from the original Church dating back to Christ, Protestants broke away from that Church during the 16th century under Martin Luther.

The reason why Catholics have problems relating to Protestants is because to some Catholics they are viewed as heretics and modernists. And for some Protestants they have problems with Catholics because they view them as not being Christians because of their traditions.

Transubstantiation of the host and wine into the ACTUAL body and blood of Jesus.

Some groups of Protestants are solely and completely focused on the Bible and Scripture alone.

Catholicism has other Church doctrine, which is not always Biblical.

and there's the celibate Clergy, Mary the Mother of Jesus as a Life long Virgin assumed into heaven at death and born with out original sin.

original sin

Saints

a Pope

There's more but those are some of the big ones.