Zombie Nation, or Samurai Zombie Nation as the in-game title screen calls it, is a 1990 NES action game developed by KAZe. In Japan, it is known as Abarenbō Tengu (暴れん坊天狗, lit. "Hooligan Tengu"). This game is known for its strange juxtaposition of zombies and samurai.
In Zombie Nation, the floating samurai head, Namakubi, is sent to the United States to destroy Darc Seed - an alien who crashed to Earth via a meteorite and turned all the American people into zombies. Namakubi must recover the samurai sword Shura and destroy Darc Seed and its minions.undefined
Version Differences
Abarenbō Tengu, meaning "hooligan tengu", was released in Japan in 1990 by Meldac. It was then localized outside Japan as Zombie Nation due to the tengu belonging to Japanese folklore not widely familiar with western culture. Aside from having some Japanese text, both games are practically identical, with this game having only a few major differences:
In Abarenbō Tengu, the player must obtain the rapid fire ability. In Zombie Nation, the player starts with it.
The main character's sprite is not that of the flying samurai head, Namakubi, but that of a Japanese konoha tengu head. The title screen is different with the tengu's head being incorporated into it.
The boss of Round I is an evil Statue of Liberty in both games but with a slightly different sprite; instead of being green with snakes in replace of its crown in Zombie Nation, it's red and has a normal crown.
Source: Wikipedia, "Zombie Nation (video game)", available under the CC-BY-SA License.