What? Which part of the US do you live in? ;)
The emergency exit icon is, as far as I know, fairly universal. I have never seen one that is non-green, nor one that differs substantially from the one you linked to.
Yes, the textual "E X I T" boxes generally use either red or green text in the US ... but that has nothing to do with the emergency exit icon.
The first aid sign I would say is a bit half-and-half. You mean the one with green bottom and a white cross, right? Well, that is also a fairly universal sign indicating first aid. The one you think of is the red cross on white bottom, which is the "red cross" sign (compare with the red crescent).
So, I guess this indicates the real danger behind assuming that icons you assume to be universal when they might not be. Or, when things you have gotten used to differ from generally accepted standards or conventions, and may therefore confuse more than provide clues.
[edited by: encyclo at 10:12 am (utc) on Mar. 17, 2008]
[edit reason] fixed link [/edit]