Which personification of the U.S. government is said to be an extension of the initials "U.S."?

Which singer led the Heartbreakers, whose hits included "American Girl" and "Refugee"? Which 1960s folk-rock group had hits with "California Dreamin'" and "Monday, Monday"? Which Detroit rocker was backed by the Silver Bullet Band? Which trumpeter led the Tijuana Brass, famous for hits like "A Taste of Honey"? The island of Tobago forms a Caribbean nation together with which larger island? Which former Beatle formed the band Wings in 1971? What name is given to the temperature of -273.15 degrees Celsius? What kind of word part is "-aceous," as in "herbaceous" or "cretaceous"?