When Jesus instituted the Supper He was in the middle of the Passover Feast. Jesus was a Jew, His disciples were all Hebrews, and so they were observing a national event in Israel. Some twenty-five years later Paul wrote 1 Corinthians which included an extensive section about observing communion. By that time the Supper had clearly crossed national boundaries. Perhaps there were some Jewish members of the church in Corinth but many were Gentiles.
Jew/Gentile fellowship is a frequent issue from Acts into the Epistles. The apostle Paul famously wrote:
For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. (Romans 1:16)
Even to mention Jews and Gentiles together would have angered Jews and offended Gentiles. Read 1 Maccabees for some history of violence. Then read the Gospels for inspired accounts of hostility. For centuries there had been bitter fights, exile and captivity and death, if not of themselves, of their ancestors. The Passover itself was a deliverance from a brutal enemy. This was a relationship with very little peace.
Yet we can look back into the earlier chapters of the story (such as Genesis 10) to see how God’s power propelled man’s fruitfulness and then pushed man to the far corners of the earth. His power established boundaries, His power caused kingdoms to rise and fall, His power sent rain and sun to grow food, His power made hearts beat. We live in a world that runs on His power and for His purposes.
His purposes include a global kingdom for His Son. God’s power created nations and God’s gospel breaks down the dividing wall of hostility between the nations (see Ephesians 2:14). So we have no need to be ashamed of the gospel. Let us celebrate His sovereign grace and His international rule through Jesus Christ, our Lord.