No, the money is not coming from a fixed box. When the US wants to do something (typically starting a new war), they never ask where the money is coming from. This tells you everything about how the decisions are made, if it is a priority for them, they will spend the money first and ask questions later. If green infrastructure was a real priority they would invest the money and later find ways to pay for it.
But those wars are typically fought to maintain the US status, to preserve its ability to debase the national currency effectively siphoning wealth from the world economy. Self-preservations comes first. I'm just describing the system.
All of them. Afghanistan as a response to 9/11, Iraq as a regional power flex and entrenchment. The first certainly preserved US status more than letting 9/11 go unanswered, the second to remove a hostile regional power and replace it with a friendlier government.
Now in Iran, the intention was to repeat Venezuela and effect regime change in a hostile country, bolstering America's military status.
Whether these wars have the effect they intend is beside the point; you're asking why they were fought, not whether they resulted in "Mission Accomplished".
