Sanctification of the Nations

Moses says:
See, the LORD your God has placed the land before you; go up, take possession, as the LORD, the God of your fathers, has spoken to you. Do not fear or be dismayed... Yet you were not willing to go up, but rebelled against the command of the LORD your God; and you grumbled in your tents and said, 'Because the LORD hates us, He has brought us out of the land of Egypt to deliver us into the hand of the Amorites to destroy us.' Then I said to you, 'Do not be shocked, nor fear them. The LORD your God who goes before you will Himself fight on your behalf, just as He did for you in Egypt before your eyes, and in the wilderness where you saw how the LORD your God carried you, just as a man carries his son, in all the way which you have walked until you came to this place.' But for all this, you did not trust the LORD your God, who goes before you on your way, to seek out a place for you to encamp, in fire by night and cloud by day, to show you the way in which you should go. Deuteronomy 1

I've always thought that the Israelites' lack of faith was strange and unexplainable. I've never understood how it was possible for these people, having been told they were the chosen ones of God and having seen His wonders in Egypt and the wilderness, could ever have rebelled and shown such an audacious lack of faith in what God could do. This was the God Whom they watched part the waters of the sea and send manna out of the sky to feed them. Yet, it seems with every test of faith they had no faith. Why?

I've heard someone say that these Israelites were completely ignorant of almost all the attributes of God; that, in a sense, God had to teach them from scratch everything He wanted them to know about Himself. They lacked, for example, any understanding of monotheism, miracles, faith, spiritual fidelity, etc. So, this explanation would say, if their faith seems to have been very immature and weak that's because it was. This doesn't seem to apply exclusively to God's people either. Many or most ancient cultures had similar worldviews.

I wonder if it's possible that as God has sanctified His Church, much of the world has also been sanctified. I see a general acceptance of Truth in cultures today, especially in America, that is much more mature than, say, three thousand years ago. For example, many or most (or, at least more) work within a monotheistic framework, accept that belief is faith and that faith must lead to action, believe in Good and Bad, believe in the need to uphold some objective standard to be deemed acceptable before whatever deity they are aiming to please, etc. We, as mankind, just seem to have a better understanding of God built into our cultures and to be more ripe for faith.

In addition, though, I wonder if one could make the case that the collective faith of the Church is now stronger and purer than in earlier history. I know that heresy is running rampant and that there are tons of false prophets running around and that Christians seem to be irrelevant and bla bla bla. But I find it amazing that most Christians would claim that salvation comes by grace through faith because of the saving work of the Son of God, Who is Jesus Christ. (I've found that, after studying more and more history, those basic doctrines weren't as common as I'd thought.)

I may be way off, but my impression is that history shows how God's truth has taken root more and more in mankind. Could this possibly be an example of God's victory in this world over Satan and of mankind's progressive sanctification?

It's probably more likely that I'm just misinformed and optimistic to a fault. Either way, let me know. :)