Contrasting Contractions

By current convention, the WWII slang terms for our enemies in the Pacific, "Jap" (short for "Japanese") and "Nip" (short for Nipponese) are generally considered to be bigoted slurs. As a decently acculturated urban SWPL Americanperson, I feel a little uncomfortable even typing them.

So, what I'm curious about is this: Are the British slang term "Yank" (short for "Yankee") or the German "Ami" (for "American") also bigoted slurs we should strike from oral histories? If not, why not?

There's a fine gradation of slurs among my fellow Cracker subtypes. "Kraut" is insulting but not totally verboten, while "Mick" and "Frog" are pretty borderline, and "Wop" is beyond the pale these days. But who keeps track of this stuff, and how does it permeate among the culture? By what process do we update our internal three-ring binders of acceptable terminology?
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