It may be simple, but it pretty much sums it up. There is no bigger factor that differentiates the US and European viewpoints.
That's always the case. The determinant of a country's politics is its culture, the determinant of a country's culture is its religion. It may seem a little too pat, but it's a reliable general rule.
Europeans, Americans, et al. who subscribe to this "high culture" deny the existence of God and the fundamental spirituality of humans, which is an inherent longing for God, as ruthlessly as previous generations denied the fundamentality of human sexuality--and with about as much success.