This chart shows the difference between the percent of federal tax receipts used to pay interest on the national debt (currently around 20% of tax receipts) and the FEDFUNDS rate. This difference has been growing through the years as the debt grows larger and people are less willing to buy treasuries at low interest rates. Even with historically low interest rates in the present day, the debt burden is large enough to over come this.
The effect of the FEDFUNDS rate on government expenditure will continue to grow with time. Even at an effective rate of 0%, the interest payments on the debt continues to grow. There is a clear upward trend on payments despite a near 0% FEDFUNDS rate. Increasing the FEDFUNDS rate will be detrimental to US government solvency. Inflation or default seem to be the two options available. Good luck, Fed people.