We study the nature of systemic sovereign credit risk using CDS spreads for the U.S. Treasury, individual U.S. states, and major Eurozone countries. Using a multifactor affine framework that allows for both systemic and sovereign-specific credit shocks, we find that there is much less systemic risk among U.S. sovereigns than among Eurozone sovereigns. We find that both U.S. and Eurozone systemic sovereign risk are strongly related to financial market variables. These results provide strong support for the view that systemic sovereign risk has its roots in financial markets rather than in macroeconomic fundamentals.