An apostle to whom? Everyone. Yes, the nations were tribes, but not always.
Paul evangelized to Jewish Christians, as he did in the letter to the Romans. Later in that letter, he turned his attention to the Gentiles and called himself an apostle to them (11:13).
Many Gentile converts followed Paul and Barnabas:
And after the meeting of the synagogue broke up, many Jews and devout converts to Judaism followed Paul and Barnabas, who, as they spoke with them, urged them to continue in the grace of God (Acts 13:43).
Luke also recorded a conversion of pagans in Ephesus to Christianity at such a rate that artisans bemoaned diminished incomes because they were receiving fewer orders for shrines to pagan idols as their countrymen abandoned these idols and turned to God (
Acts 19:23-27). Paul was in Ephesus at the time helping to turn these pagans away from their old customs.
In 1 Corinthians he preached to former pagans again, calling them brothers (12:1-2).
Paul also unabashedly preached the gospel to epicureans and stoics, some of whom converted (
Acts 17:18-34). Epicurean and stoic philosophers were pagans.
Paul, in fact, even hinted to the Colossians that former pagans at certain times and places in the middle of the century not only counted themselves among the Jewish converts to the faith but also outnumbered them. On at least one occasion, he could name only three Jews who worked beside him among all the workers in his ministry to advance the kingdom (4:10-11). He seemed to be reaching more pagans than Jews.
