Why do most Americans take a shower after they wake up in the morning?

I'm Chinese. What I know is that nearly all Chinese people take showers at night. Why do Americans take a shower in the morning which drives them to wake up earlier? And I also want to know which countries take a shower in the morning like America, and which countries take a shower at night like China.

I'm an American-born Chinese who has lived in China for a total of over 20 years, so this is a question that I get all the time. Among everyday habits and, the shower-in-the-morning vs. shower-in-the-evening is one of the real lines of demarcation between Chinese and westerners, and neither my Chinese-born parents (who never lost the evening shower habit even after 40 years in the US) nor my wife, who's from Beijing, ever get tired of asserting the supremacy of the PM shower. And I've never kicked the AM ablutions habit.

I shower in the morning because it really wakes me up, and provides me with this nice mindless routine during which I can think about my day. It also keeps my hair from looking strange. On warmer days where I've conspicuously sweated during the day I'll take a quick shower and not wash my hair in the evening, but I find that taking a shower right before bed makes it more difficult for me to fall asleep, possibly because I associate showering with wakefulness.

I fully understand the Chinese preference for the evening shower. You're clean and comfy, bedding probably doesn't need to be washed as frequently and so forth. But I just need that morning shower to feel fully awake—kind of like that morning coffee!