Time Out says
After the cult successes of Sid and Nancy and Repo Man, somebody thought it a good idea to give director Alex Cox the money to make a historical epic. While that person probably spent much of 1987 and 1988 kicking themselves—the resulting film, Walker, barely got released—we can now see, two decades hence, that it was an inspired idea.
William Walker (Ed Harris), an American adventurer who, with the backing of wealthy industrialist Cornelius Vanderbilt (Peter Boyle) led a bloody revolution in Nicaragua in the 1850s and had himself declared its president, was an actual person. But Cox and screenwriter Rudy Wurlitzer take small liberties with the facts: We’re talking about a Victorian-era film in which characters read Newsweek and a chopper full of Marines comes to save the day. That said, the Criterion edition comes with a booklet that outlines the film’s surprising level of accuracy (other notable extras include a commentary track by Cox and Wurlitzer).
As portrayed by Harris, Walker is a pious, steely-eyed buffoon who talks of listening to a “higher power” and is completely taken with the notion that he’s bringing the American way of life to Nicaragua. He’s not a cynical, calculating villain, but rather a bizarro version of the classic Western hero: an idealistic dolt who refuses to see the error of his ways. Is this starting to sound familiar? Cox’s blood-soaked cri de coeur says as much about our desire for heroes as it does about our villainous ways.