Your problem is you think you can not be deceived about anything, so your adding to the word something that is not there
the word can mean gentiles or nations, you assuming it just means people, but that makes no sense, Satan is not omnipresent, he does not go around wasting his time trying to decieve people, he decieved countries, like he has been doing since the beginning, countries like the Islamic countries that prohibit and kill christians, and teaching their children against God
and the passage does not say faith in Christ stops people, it says satan is bound in the bottomless pit so he can not deceive
your missing the whole point of what is being said, christ rules, the nations live in peace, everyone knows who he is, at the end, he is freed, and immediately again gathers an army, even after people have witnessed the goodness of God for 1000 years.