Europe as we know it is slowly going out of business. Since French and Dutch voters rejected the proposed constitution of the European Union, we've heard countless theories as to why: the unreality of trying to forge 25 E.U. countries into a United States of Europe; fear of ceding excessive power to Brussels, the E.U. capital; and an irrational backlash against globalization. Whatever their truth, these theories miss a larger reality: Unless Europe reverses two trends — low birthrates and meager economic growth — it faces a bleak future of rising domestic discontent and falling global power. Actually, that future...