Whether or not we can, we should evangelize the nations as if we can.
A common criticism I've heard is that God would be unjust to condemn a person to hell if they never had the opportunity to hear the gospel. Some people think that the "savage in deepest, darkest Africa" who never had a missionary tell them about Jesus would still be saved by God's grace in spite of their unbelief. But there are too many places in Scripture that disprove that idea. I now understand that God is not solely dependent on us humans to reach the lost for Christ. He is perfectly able to overcome any and all obstacles standing in the way of a person who seeks Him. How one responds to the light determines how much more he is given. I was just as lost as that "savage" living right here in America even though I was raised in a religion. But I asked God to show me the truth and He did. It is God's will, after all, that ALL be saved and come to the knowledge of the truth. No one will be in hell who can claim they never had a chance to hear the truth.