The speed with which persistent imbalances in EMU can result in systemic risks was not fully understood prior to the crisis. An important lesson is that due to high trade and financial integration in the euro area, the build-up of imbalances in any individual euro area country increasingly affects all others. In other words, there are greater spillover effects on account of increasing interconnectedness.
In 2010 and 2011, almost all of the mortgage-backed securities (MBS) issuance in the US has been by the agencies. As you recall, the agencies purchase eligible loans from mortgage originators (including banks) and either keep them on their own balance sheets or pool them into MBS to be sold to investors.