Most Christian congregations have an ethnos, a term from cultural anthropology for people with a common national or cultural tradition. Congregations are usually part of a larger network, denomination, or hierarchy, which has at least one ethnos. (Eastern) Orthodox autocephalous churches are national churches, which include the ethnos of their nation. The (Roman) Catholic church incorporates multiple national churches, each with its own ethnos. In places such as the U.S., a Catholic parish reflects the ethnic background of the parishioners, usually Italian, Spanish, Irish, or Polish.
Protestant denominations reflect their national origins. Lutherans have a Germanic or Scandinavian ethnos. Presbyterians have a Dutch, Scottish or Swiss ethnos. Anglicans have a strong British ethnos, which includes the Queen. Many denominations adopt the ethnos of the country they reside in, so for example American Baptists have an American ethnos. The Messianic congregations springing up have a Jewish ethnos.
A church ethnos reflects the way that Christianity is a universal religion that does not replace the ethnos of its adherents. The original Christian church had a Jewish ethnos but as Gentile believers became dominant, Christianity acquired the ethnos of the nations. The apostolic decision that Gentiles did not have to be circumcised or keep the Jewish law affirmed Gentile national customs and laws.
Some worry that a church ethnos may be excessive or even idolatrous. While that is possible, church and ethnos have been together for centuries without significant harm. The excesses that have been pointed out, such as the Russian Orthodox under the Czars or some Lutherans in Nazi Germany, have come and gone. And the Lutheran Confessing Church was a witness against an excessive ethnos in the church.