A few reasons why your economies are screwed even if you are "self-sufficient" in terms of Oil and Gas:
You are completely cut off from the most vital shipping lanes in the world. Any goods you do manage to import will be a significantly more expensive. This will, in turn, lead to higher levels of Inflation. Very high inflation means people lose a lot of their savings. People who just lost their savings tend to cause instability. Instability will further hurt the already weak economy. An even weaker economy, will lead to even more instability. Downward spiral....