The use of stopgap funding measures to keep the U.S. government open amid frequent political squabbles over how to tackle rising national debt carries long-term risks for the world's largest economy.

While the ongoing stasis in Congress has yet to do any serious damage to the buoyant U.S. economy, the regular budget standoffs — and the failure to tackle the country's growing debt burden — are already having an impact.

Two out of the three major American ratings agencies have now cut their credit rating for U.S. government debt, while Moody's, the sole holdout, recently downgraded its own outlook.