American Self-Defence Law - Help Needed

Well, I'm no expert, but here are three links that may help--the first gives an overview of self defense law in California from a lawyer's standpoint, the second is an excerpt of California law pertaining to when homicide is justifiable, and the third is a link to search results for all snippets of California penal code pertaining to self defense:

http://www.shouselaw.com/self-defense.html

http://wings.buffalo.edu/law/bclc/web/calpenalcode197.html

http://www.leginfo.ca.gov/cgi-bin/calawquery?codesection=pen&codebody=se...

As Wastelander linked to, California state law will be most important.  Within the US, each state has differing statutes involving self defense.  Getting familiar with them will be important.  As someone said else where though (knife defense forum perhaps?) remember that you will go a long way toward obeying self defense laws if you do the following: "Don't got stupid places and do stupid things with stupid people".  There are plenty of details to go with that, but it's a good base guideline I find it hard to argue with.