As the language has evolved, Guys here in Australia can refer to everyone as a group(gender neutral) and is popularly used by both men and women, although some object to it OR a group of men, whereas guy in it's singular form is gender specific. Not sure how it is in Nebraska.The "you guys" example seems a bit odd. If they'd said "guys and girls", I'd understand, but surely simply saying "you guys" implies that it's referring to everyone and not just one gender?
Anyway, I went to an all boys school so saying "you fucking cuntholes" was pretty common, which was also mostly gender neutral.