[en.wikipedia.org]

They don't work appreciably more than people in the U.S.

Also:

"The United States is among the most homework-intensive countries in the world for seventh- and eighth-grade math classes. U.S. math teachers on average assigned more than two hours of mathematics homework per week in 1994-95," said LeTendre. "Contrary to our expectations, one of the lowest levels was recorded in Japan -- about one hour a week. These figures challenge previous stereotypes about the lackadaisical American teenager and his diligent peer in Japan."

From: [www.physorg.com]

It's crowded, but not everywhere. In general the various prefectures have higher population densities than U.S. States, but there are several prefectures whose densities are "comparable" to states like Maryland (222 people/km-sq) and Florida (130 people/km-sq). It just doesn't drop much lower than that, whereas in the U.S. you have states like Texas whose density is 35 people/km-sq.