The difference between Christianity and Catholicism

[Creaky]

There was no formal church, no. 
No formal creed,
no formal set of books that everyone used.  There was a lot of fierce infighting over whose rules should be followed, but the consensus of the majority of the groups of believers is the practice that became the Catholic Church.

Minority groups like the Essenes did not have many of their ideas adopted. 

Other minority groups were eliminated (often in warfare.)

But the original faith that swept the world was that of the Catholic Church.  Protestantism is an evolution from that, but not an evolution that took place by going back to original manuscripts and trying to find what the original practices were.  So, yes, it's not what the originators would have recognized.

there were plenty of formal churches pre the Nicene council, plenty of denominations, not sure how you can deny that
The apostle Paul’s letters clearly indicates such

if you mean catholic as in a universal faith belief, ok I agree
if you mean catholic as Roman Catholic, nah, 

no creed, so what, I am non creedal Christian. I don’t need a creed

Rome was not and still is not the centre of christianity, Jesus is
Constantine didn’t end christian persecution till 300ad, so how Rome had a pope is a little ridiculous, read that again Byrd

rome catholicism did not sweep the world, it conquered the world with swords and blood, under Roman military power, no wonder people hate christians 
The opposite of Christs teachings

As for original faith teachings
the pope changes Roman catholicism as required, a bulla here, there, anywhere, especially when more money was required. Not unlike Jehovah Witnesses of recent

at least the Protestants went back to the bible, the original transcripts, manuscripts and teachings
yes, Protestantism has many issues, no denying
I can say that as my faith is not in man or the church itself, my faith is in Jesus