Lets stop right there for a minute. There is no word in the original Greek used to write most of the New Testament that can realistically be translated church. There isnt even a word that gives the concept of what most people think of as church today. The word church comes from kyridakon and is not found at all in the New Testament. The word that has been erroneously translated church is ekklesia and really had nothing to do with Christianity or religion per se. It simply meant a called out group. It was used for most any assembly of people whether they be civic or whatever.
What Christ was saying in Matthew 16:18 was that He was building His called out group of people and He was building that on the fact Peter had just stated, that He was the Christ, the Son of the living God. No where in the New Testament was there any commands or instructions of building some hierarchical structure the all of the denominations, including the Catholic Church, use today. Each local assembly was autonomous other than under Christ who is the head of all of the assemblies of believers. There is no reference in all of the New Testament of the universal church or even a universal assembly other than in Revelation when it is called the bride of Christ. Paul wrote to the ekklesia in different locations but never referred to what people today think of as the universal church because there wasnt one and there isnt one today that is sanctioned by Christ. The universal church is a man made concept and does not come from scripture.
In Revelation 2:6, 15, God said he "hated" the Nicolaitans who sought to set up a hierarchy to rule over the people. A study of the word Nicolaitans shows it to mean the bishops of the assemblies gained a victory (Nico) or conquest over the Laiton or the laity. Members were compelled to submit to the dominion of men. God states that that is something He hates. That describes all of the "denominations" today and in particular the Catholic Church.
Once people begin to realize that and stop following man perhaps they can begin to realize the error that exists in the concept of church today. The concept of the universal church is nothing more than a man made construct to usurp the authority of Christ and impose control over people.
The Bible defines “church” as two or more people coming together to worship God.