BEIJING — The American ambassador to China, Terry Branstad, wanted to make what in most nations would have been a routine trip.

One of his favorite schools, Iowa State University, had opened a center to promote American culture in an inland Chinese province, and the laid-back former governor of Iowa was eager to take questions from Chinese students.

The center’s program, largely financed by the State Department, was deliberately benign so as not to offend Chinese government sensibilities. Politics was off the agenda. English lessons focused on fashion, music and sports. An essay-writing contest was called “Bald Eagle & Panda” after well-known fauna in both countries.

But Henan Normal University, a campus set on the Yellow River with a prominent statue of Mao Zedong out front, denied Mr. Branstad permission to visit the center this fall — and offered no explanation.