CARACAS—Shortly before announcing that Hugo Chávez died, Venezuela's government resorted to one of the late president's favorite ploys to try to unite his supporters: allege a conspiracy by the U.S. to destabilize the country.

Vice President Nicolás Maduro kicked out two U.S. military attachés for allegedly plotting against Venezuela and even suggested that Washington may have been behind Mr. Chávez's cancer.

"Behind...