"Ziehan predicts the demise of many countries but not the demise of the United States which essentially faces the same problems other countries face: a birth rate that is so low, it fails to meet population replacement levels."

You are correct but unlike other countries the low birthrate won't hurt the United States for 30 years! Gen Y in the United States is LARGER than Gen X. That is not the case in other industrialized countries and gives the United States an enormous advantage. The U.S. will suffer in 2020 when the majority of baby boomers retire (big recession or even great depression?) but then things look bright again as gen Y really starts earning and paying significant taxes. That isn't the case for the rest of the industrialized world.