Peter, first chosen of the apostles, having been apprehended often and
thrown into prison and treated with ignominy, at last was crucified in
Rome.
Catechism of the Council of Trent (1566)
The Catechism of the Council of Trent did not directly refer to the question
of whether St. Peter had ever been in Rome, but in Pt. I, Ch. X quotes the
following from Optatus of Milevi (De Schism. Donat. ii. 2):
You cannot be excused on the score of ignorance, knowing as you do that
in the city of Rome the episcopal chair was first conferred on Peter, who
occupied it as head of the Apostles...
Catechism of the Catholic Church (1992)
Likewise, the Catechism of the Catholic Church makes no direct statement
on the question of whether St. Peter ever visited Rome, but re-affirms that
the Pope is the Bishop of Rome and Peters successor (No. 882).