China and India have the same amount of people.
While China has 3 times the area of India, China's population is jammed into the eastern third of the country.
The result is a similar area with a high population density:
I was in China for 3 months last year, in the eastern-most part of the bulge. This included Shanghai.
Crowded? Yes. But no more so than New York City. The difference in Shanghai is that the skyscrapers went as far as the eye could see.
America has 4 cities with a population over a million; China has 125
American cities are typically surrounded by suburbs; in China the landscape goes from well-planned urban settings to rural squalor rather sharply.
The air and water pollution was very bad in China everywhere.