Who was the first Christian in Rome is irrelevant, who was the first bishop or Apostle who had authority over it is what matters. The Bible gives sketchy clues that Peter was, in fact, in Rome. This is confirmed by the historical record that you deny.
1 Peter 5:13 - Some Protestants argue against the Papacy by trying to prove Peter was never in Rome. First, this argument is irrelevant to whether Jesus instituted the Papacy. Secondly, this verse demonstrates that Peter was in fact in Rome. Peter writes from "Babylon" which was a code name for Rome during these days of persecution. See, for example, Revelation 14:8, Revelation 16:19, Revelation 17:5, Revelation 18:2,10,21, which show that "Babylon" meant Rome. Rome was the only "great city" of the New Testament period. Because Rome during this age was considered the center of the world, the Lord wanted His Church to be established in Rome.
2... Then I laid before them (though only in a private meeting with the acknowledged leaders) [the Apostles] the gospel that I proclaim among the Gentiles, in order to make sure that I was not running, or had not run, in vain. [Paul validates his gospel with that of the Apostles, not the other way around]3 But even Titus, who was with me, was not compelled to be circumcised, though he was a Greek. 4 But because of false believers secretly brought in, who slipped in to spy on the freedom we have in Christ Jesus, so that they [unconverted Jews] might enslave us— 5 we did not submit to them [unconverted Jews] even for a moment, so that the truth of the gospel might always remain with you. 6 And from those who were supposed to be acknowledged leaders (what they actually were makes no difference to me; God shows no partiality)—those leaders [unconverted Jews] contributed nothing to me. Paul verifies his gospel with the Apostles gospel and you would have us believe Paul did not submit to the Apostles, they might enslave us, contributed nothing to him, etc. You can't see the distinctions between false Jewish leaders and the Apostles.
You dishonestly chopped a sentence in half. There are some things in them hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other scriptures. [like you did with Gal. 2] Is Peter saying he is too ignorant and unstable to understand Paul?
Acts 15:12 - only after Peter (the Pope) speaks do Paul and Barnabas (bishops) speak in support of Peter's definitive teaching.
Rom. 15:20 - Paul says he doesn't want to build on "another man's foundation" referring to Peter, who built the Church in Rome.
1 Cor. 15:4-8 - Paul distinguishes Jesus' post-resurrection appearances to Peter from those of the other apostles.
Gal.1:18 - Paul spends fifteen days with Peter privately before beginning his ministry, even after Christ's Revelation to Paul.
It was an oversight. I was wrong.