Skullcrusher mate, you might be American but I am British, hence the British flag. My wife's American and we live in America now, but I'm still allowed to be a little patriotic once in a while... hope you don't have a problem with that
Don't see why anybody should be offended by it... our countries have been great allies for centuries. I see plenty of American and Canadian flags on forums all over the place... and I wouldn't think to question it.
Anyway guys, some good answers on this post, thanks for humouring my wacky scenario, it was just my way of putting a little background story to your decision to pick a survival gun. I know some of you found it funny, but it looks like it turned out to be a pretty popular thread, with some good answers.
Myself, I'd probably settle for a 12 gauge or 9mm carbine. Of course, given the option, it would be best to carry a sidearm too... I'd grab a Sig P226 and a sturdy combat knife such as a Ka-Bar with partially serrated edge.