The gospel of Jesus Christ is the good news of salvation. Jesus has given us (his church) marching orders to take this gospel to all peoples. We should take careful note that our Lord has given this commission to one people and for one people.
Jesus has commissioned his entire church. In this sense, he has instructed one people - his church - to work together to take the gospel to all the peoples of the globe. Jesus did not tell some of his followers to be concerned with this task, while telling others to ignore it. Rather, he clearly expects all to be involved. This may look different from person to person, but in the end all are united in accomplishing the task. John chapter 17 is one passage among many where Jesus emphasizes the importance of the unity of his people.
The reality is that, in the USA at least, the church is not united in the Great Commission. Various denominations and sending agencies work separated from each other in reaching the lost. Thousands upon thousands of dollars are spent on repetitive tasks that would be unnecessary if the agencies/denominations worked together. While many missionaries in the field do work together, their churches and agencies back home often do not. It would benefit the church greatly if denominations and non-denominations would make more concrete efforts to pool their resources, cut costs, and target unreached people groups more systematically.
Just as Jesus expects us to be united as one people, he also desires that we work together for one people. That one people is all the peoples of the globe. The gospel is not just for the Jews. The gospel is not just for Europe. The gospel is not just for large groups of people. The gospel is for all people. It would be easy to simply target some groups to reach with the gospel. However, the call is for all people - even those who may be violent, those who may be poor, those who may live in remote places, those who may speak languages that haven't yet been written, those who may not want to hear about Jesus, those who may eat weird food, those who may smell, etc. They all must hear.
We cannot as a church pretend that we lack information. Sites such as Joshua Project and People Groups provide bucket loads of data about peoples who have yet to hear about Jesus Christ. The real questions are whether or not we are willing to sacrifice and whether or not we are willing to work as one church to reach the lost.
In God's eyes his people are one people. Let's live like it while reaching those who are not yet part of his body.