Jesus created his Church. Man created Denominations. Before the various splits due to Luther and Henry VIII, there was a single church, the Catholic Church.
Also, no Catholic with a real understanding of his faith would ever claim that Catholics are the only believers. We do believe that we have the fullness of the faith because we have the entire body of revelation through Scripture and Sacred Tradition. That doesn't mean that non-Catholics do not have at least that part of revelation provided by Scripture.
There were splits long before Martin Luther, in fact, the institutional church as we se it today is a split from the local Church idea the APostles started.
THere were many local churches that never fell under the control of Constantinople or Rome, and they remained local churches until they were persecuted to death.
That means the RCC, the Orthodox, the Asyrian, they are all splits from what God started:: Individual Churches for each city, local control, Bible based values, not man created rules or spelling out of doctrines.
The Reformation was a feeble attempt to return to Biblical truth, but Protestntism never fully went back to the original ideas.
Bible churches are close, but as far as doctrine, you have to shop around for a good one among them, also.
But, a denominational Church, thatis totally not what God started,and there is zero evidence He did.