So wouldn't the solution to this be to not transfer the money between countries? Ie. have a different exchange in each country and then an exchange would only need to store (and not transfer) the users' funds.
no, the problem is not transferring money to another country, the "problem" is storing your value, your credit, like a bank.
when you transfer 200 $ to mtgox , you got a credit of 200 $ in mtgox, and you can also withdraw them, they are attacking on this point, storing money, to make it simple.
P2P exchange would be a good solution...and probably one that no govt would be able to stop...orders need to be announced on a p2p network with matching engines that pair up orders and find a ripple like path to transfer personally issued debt coins. A distributed routing protocol (similar to BGP) could find optimal paths of credit through the ripple network. Orders could include a fee that the matching engines collect. Nodes can monitor the order flow to piece together an order book. Super nodes in the ripple network could connect lots of users to one another (super nodes could allow people to purchase a certain amount of credit). People settle up their debts as desired. The first step would be to figure out how an order would look (which would be partially completed transactions) and how a matching engine would finalize the transactions.