BEIJING—A sweeping evacuation of American diplomats has hobbled the U.S. government’s presence in China, further rupturing interactions between the two superpowers at a time of rising tensions and hampering efforts to fight the coronavirus pandemic.

U.S. diplomats and their family members started to return home en masse in early February as coronavirus infections exploded, kicking off what has become one of the largest peacetime evacuations of U.S. diplomatic personnel in history.

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