Yu Zhijian, 53, died on March 30 of complications related to diabetes, his widow Xian Gui'e said by phone from their home in Indiana state.
"Yu Zhijian never regretted what he did in 1989 but he would have liked to apologise to Mao's family for throwing eggs on the portrait," she told AFP.
The Tiananmen pro-democracy movement ended in bloodshed on June 4, 1989 when tanks crushed the demonstrations, killing hundreds of protesters.
Yu was sentenced to life imprisonment after the brutal crackdown and was eventually released for good behaviour in September 2000.
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He and his accomplice Yu Dongyue, released in 2006 after 17 years in prison, fled China in 2009 after obtaining political asylum in the US.
A third man also involved in the ink-throwing incident, Lu Decheng, fled overseas in 2004 after his release in 1998.
Xian said that her husband obtained US citizenship and worked as a caregiver.
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