【答案解析】本题要求判断“美国人欠觉”这一结果是由何种原因导致的。依据文章第一段第二行There's even a prohibition against admitting we need sleep Nobody wants to be caught napping or found asleep at work，依据文章第二段第一行We have to totally change our attitude toward napping．说明美国人缺觉是因为美国人对睡眠的传统观念有问题。故A正确。