Acts of "irresponsible spending" by Congress can have several different effects on America's future. Here is a list of just a couple possibilities.
1) Increase America's debt- If the federal government spends more money than they initially budgeted, this could cause debt. Debt is usually bad for the American economy, as it causes the US to borrow money from other countries or institutions. From there, the US will spend a significant amount of taxpayer money trying to pay back this debt.
2) Cuts to government programs- If the federal government spends recklessly, this may cause them to cut funding to different federal programs.