This may come as a surprise to US citizens, who can vote postally wherever in the world they may currently reside, but that's the way Wee Eck wanted it, so that's the way it's going to be!
But then, once a US citizen you always remain so in that you remain liable for US taxation irrespective of where you live.
Watch out the Scots, double taxation, as per the USA, may be deemed necessary!
Seems to me that the Scottish Separatist movement is being orchestrated by someone with a personal grudge against England and therefore a personal agenda. I have seen no evidence of a post separatist strategy to finance Scotland. Many repetitive, stonewalling answers from the sour-faced Salmond, but no sign of a policy and no business plan. If there is one, he has perhaps deliberately kept the less than palatable detail out of the equation.
The voters should take into consideration that this will truly be an occasion when the phrase "you deserve what you voted for" is very, very, appropriate.
Then watch out for the asylum seekers / economic migrants come clambering over the newly rebuilt Hadrian's Wall in years to come......