The United States revoked the visa of Venezuela’s ambassador to Washington in retaliation for President Hugo Chávez’s rejection of an envoy nominated to be the American ambassador in Caracas, the State Department said Wednesday night. Mr. Chávez had blocked the arrival of the American diplomat, Larry Palmer, after Mr. Palmer accused the Venezuelan government of having close ties with Colombian rebels. In response, the United States effectively expelled Venezuela’s ambassador, Bernardo Álvarez Herrera, by withdrawing his visa.