From China Law Blog:

The National Football League (NFL) will be putting on a preseason U.S. football game in China this summer as a platform to increase China's awareness of the game. Waller describes China as an "incredibly exciting" market, for the NFL and for other sports leagues.

The National Basketball Association (NBA) is the most popular sports league in China and more than 300 million people in China play basketball.

The NBA has its website translated into Chinese, the NFL does not.

This site explains why basketball is the most popular American sport in China, having a following much stronger than any of the other American sports.

Five years after Dr. James Naismith invented the game, missionaries brought it to China. Although China has been through many cultural and social changes throughout the past century, basketball has remained a popular pastime to many. And its popularity has significantly increased with the rise of Yao. A 2003 survey showed 75% of Chinese males between 15 and 24 years old were interested in the basketball, says Tan Kefei, editor of the new basketball magazine Ally Opps. Many fans are now obsessed with tracking Yao’s progress in the US, and NBA games are televised on 14 Chinese channels, including state-run CCTV.