The United States has over 300 million people. Only about a third claim to be born-again evangelical Christians. Meaning, at absolute best, we have 100 million people who are saved in the nation. And that would be a very "high" estimate. It would be my contention that the idea we have over 200 million people in our nation that are destined for hell, we should begin to look at the United States as a great mission field.
I live in North Carolina, which is part of the so-called "Bible belt." At work, there are about 40 people in my department that I work with. There are a few who claim to be Christians, but, clearly are not. I don't know for sure, but, I may just be the person who is saved in the entire department. There is perhaps one or two other people who might be. But, because of the nature of my work, I don't get a lot of opportunity to mingle with my co-workers, except for those who sit immediately around me.
And having worked at several places in the last decade, this has been very typical. If I work at a place with 100 people, there might be 3 or 4 truly saved Christians. And then, they are usually pretty spiritually immature. If things are like this in North Carolina, I can only imagine what it is like in the rest of the country.
Instead of churches sending people overseas for mission trips, we need to start looking at our own back yard as a mission trip. But, many Christians who are willing to go overseas and share their faith are paralyzed with fear with sharing their faith in their own backyard.
I believe God has one day called me to be a "missionary" to Greensboro, NC. Me going forward to do that work is still years away. But notice I said the word "missionary." And that's the word God used when he called me for that task. When he finally sends me, I will operate out of that understanding.
*edited*