Simple: Our constitution, our legal framework that (mostly) protects us from corruptive forces, our ability to trust that sellers can't sell us poison and lie to us about it, our ability to enter into transactions with total strangers without worry, our free elections, our freedom of expression, freedom of association, freedom of movement, freedom to be who we are.
People are stumped because they're not looking at it for what it is. There's no mysticism wrapped around our secular societies like there are around religions, so people tend to not notice it. But if you look at it - REALLY look at it - it's nothing short of miraculous what we've achieved. Life before we had these things was VERY, VERY different from the peace and prosperity we've enjoyed for almost a hundred years.
And it's unfortunate that people have become so entitled and myopic that they've lost sight of it to the point where they actually favor strongmen as heads of governments...
Don't it always seem to go, that you don't know what you've got till it's gone.