Non-procreation is not the root of the problem, it is a consequence. West has lost its identity --- first, having lost faith in G-d since the Enlightenment; and then having acquired post-colinianl guilt. We in the US are equally sick but are slightly behind the Europeans. Our elites have succeeded in teaching great many Americans that everything Western in evil --- individual liberties, history, free markets... At this point, most hardly know history or what individual liberties (as opposed to civil rights) and free markets are. And nobody never defend what they don't know. Unless Martians become enamored with our Constitution, I don't know who is going to defend, or even uphold, in the next generation.
Either one, they still aren’t procreating as fast as the Muslims.