The sign in front of my former Roman Catholic parish proudly proclaimed that it was “Roman” Catholic. Also, the entire Catholic Church is headquartered in Rome.
The term “Roman Catholic” was used by Anglicans in the 1800s who were starting to identify themselves much more with the historic, sacramental heritage. So they called themselves as patriotic Anglo Catholics, to differentiate themselves from those others, who suspiciously followed a foreign monarch - those “Roman” Catholics. To this day, it tends to be used mainly in English speaking countries, only in places where the word “Catholic” has been taken by many other groups.
No one is just “Eastern Orthodox”. A person may belong to, for instance, the Serbian Orthodox Church. That Church ministers to people in Serbia, or in other countries where Serbs have migrated to. They don’t refuse persons who are not Serbs, but don’t go out of their way to evangelize them. Their church is closely tied to the heritage of a specific country (but primarily to the gospel, of course). Each of the EO churches has a specific identified cultural identity. Evangelization outside that culture is permitted, but limited.
The Catholic Church is not “Roman” in that sense. It evangelizes in Africa as readily as in Italy. Most Protestant denominations in the US are heavily “Americanized”. Yes they do send missionaries to other countries, but they are very much headquartered in the USA, with all the headquarters staff permanently from the USA, often reflecting one particular region or subculture of America. Protestant denominations in the US were either founded here from scratch, or else people from Europe gathered into their own American version, with, today, only the slightest relationship with their counterparts in other countries. They are American organizations, even if they have the term Presbyterian, Methodist, Lutheran in their title.
The Catholic Church’s headquarters are in Rome, but most leaders are not from Italy. The bishop of my diocese was appointed by the Pope, not by anyone in Washington. The Catechism I use, the Code of Canon Law my priest uses, had to be translated into English. How many Protestants today use a catechism that had to be translated into their own language? The Catechism also had to be translated into Italian, because it wasn’t written in Italian. Very few official church documents are.
The Catholic Church is not a denomination.