Since Gunnison covers only 3 sq. mi., Colonel Stevens's map is showing a "pressure damage" radius of barely 1/4 mile. In reality a 200KT nuclear explosion would level all structures within at least one mile. The "heat damage" radius on Stevens's screen is even more understated.
In the commentary for Aliens vs. Predator: Requiem, the Brothers Strause point out that the bomb dropped in the movie was incorrectly displayed as a "MK83." On the screen showing the purported "damage assessment" of the tactical nuclear weapon, in the lower part of the screen the bomb is designated as a "MK 83". In actuality the Mark 83 is not a nuclear weapon, it is a conventional weapon with a modest amount of high explosive inside. It would not be capable of the damage estimated on the readout.
According to the "Goofs" section of the AVPR article on imdb and the B83 article on Wikipedia, the correct designation of the nuclear weapon is a B83. Though the B83 can produce a 200 kiloton explosion, the article states that it weighs 2400 lbs and is carried externally on the F-22. The F-22 is typically equipped with two 1000 lb JDAM equipped bombs in its internal weapons bay.