The problem with running federal budget deficits and adding to the US government debt is that the amount of the budget that is needed to pay the interest on the debt can crowd out money needed for essential programs. This is similar to a household with a lot of consumer debt.
As of the end of Fiscal Year 2020, the US Government debt was around $27 trillion dollars, however, some debt is owed to other federal agencies and this debt does not impact the interest on the debt.
The below table shows past and projected public debt and the percentage of the budget needed to pay it. (Source: https://www.thebalance.com/interest-on-the-national-debt-4119024 )
In the fiscal year 2022 interest expenses are 8.0% of the federal budget. This doesn’t sound too bad, but if interest rates were to rise as they are projected to do, then the percentage of the budget needed to make interest payments will slowly rise. Another risk is a stagnant economy in which more fiscal deficits are needed to provide stimulus to the economy and provide a safety net for the economically disadvantaged. Of course, the ultimate risk would be if the United States would have to increase spending to fight a war.