Gui, who was known for publishing salacious titles about China's political leaders, was snatched while on a train to Beijing in February 2018 and this week sentenced on charges of illegally providing intelligence abroad.
"We call on the (Chinese) government to release him immediately and unconditionally," State Department spokeswoman Morgan Ortagus said in a statement that "strongly" condemned the sentence.
"We will continue to stand with our partners and allies to promote greater respect for human rights and fundamental freedoms in China," she said.
Gui was born in China, which does not recognize dual citizenship. Chinese officials claimed he voluntarily reinstated his Chinese citizenship in 2018.
Sweden says he remains a citizen, as renunciation requires an examination and decision by its migration agency, and summoned China's ambassador on Tuesday to demand his release.
China called off two business delegation visits to Sweden after its culture minister defied Beijing's threats and awarded a rights prize to Gui in November.
Gui earlier vanished in 2015 while on vacation in Thailand, resurfacing in China where he appeared on state television confessing to a fatal drunk-driving accident and served two years in prison.