The crisis lent new urgency to something that had already been obvious before: in banking and finance, national borders are far less relevant than in other areas of life. Such an integrated financial system is certainly desirable for all the well-known reasons, including efficiency gains and risk-sharing.
However, that which distributes gains among all of us in good times, forces us all to share the pain in bad times. In an integrated financial system, problems in one country can quickly spread to others.