From one man he made all the nations, that they should inhabit the whole earth; and he marked out their appointed times in history and the boundaries of their lands. God did this so that they would seek him and perhaps reach out for him and find him, though he is not far from any one of us. Acts 17:26-27
From the context, nations refer to people groups and not countries. Most countries of the world have different ethnos (people groups) living in them and are differentiated by culture, language etc. God created the different people groups from one nation or race.
The story of the building of the tower of Babel in Genesis 11 gives us the beginning of the different people groups. Each people group has a claim to an estate they call home. Modern day travels and communication has shrunk our once big world into a global village with people virtually from every nation temporarily or permanently relocating among other people groups.
This is not accidental. It is God’s immigration policy aimed at giving people opportunities to learn about Him and be saved. People relocate because of famine, war, studies, trade, work, etc. but God uses that to place believers among unbelievers for the sake of the Gospel.
You, as a Christian, are where God wants you to be, to thrive in your walk with Him and share the Gospel with the unbelieving neighbor He brought to your doorstep. How are we doing with this responsibility?