Let's say that America followed the Keynesian theory flawlessly and always used the government to intervene when a recession was taking place. How often would the secondary effects build up every time the government would constantly spend? It seems like different factors would take place depending on the state of the economy at that moment.
Clarify this question in class if you like. The government always uses spending to intervene in an economy. The argument from classical economists is that government spending slows the growth out of the recession via the crowding out theory. This argument is a counterfactual, but the theory makes sense a priori.