Dedicated to "Lucio" (Fulci, the Italian horror director).
The ending is a reference to the ending of Lucio Fulci's Paura nella città dei morti viventi (1980). The Lucio Fulci dedication before the end credits confirms this.
Sam:
Don't be afraid, it's only friendly fire.
Revealing mistakes: When Sam is blown away, the support wires are visible. In fact, when his body leaves a hole in the house, the wires also leave a linear hole in the house.
Continuity: Uncle Sam's pants go from red and white to black and white just before the final showdown.
Factual errors: Cannon balls like those being fired from the cannon by Jed do not explode, let alone explode a half dozen times as Leslie's home did.
References
Paura nella città dei morti viventi (1980)