I don’t know about the ECB. In the U.S. Congress writes laws that control the fiscal imbalance – spending on government programs and taxation. The Federal Reserve controls the money supply using a variety of methods. Only during crisis does the Fed act as a lender of last resort (e.g. QE during the 2008 financial crisis and 2020 Covid crisis). The fiscal deficits are financed by sale of Treasuries (government debt).
History is filled with examples of governments that overspent their incomes to the point of self-destruction.
Wendy