Whether humans hear the Gospel or not, all are without excuse. The things seen were created by the unseen. They know the things seen are not created by man.

"God’s wrath is being revealed from heaven against all the ungodly behavior and the injustice of human beings who silence the truth with injustice.   This is because what is known about God should be plain to them because God made it plain to them. Ever since the creation of the world, God’s invisible qualities—God’s eternal power and divine nature—have been clearly seen because they are understood through the things God has made. So humans are without excuse." ~Romans 1:18-20 CEV


Common English Bible (2011). Nashville, TN: Common English Bible, p. Ro 1:18–20.