The US could very causally spend a couple $100B less on their military and not have a real reduction in capability.

> $100 billion spent on nuclear power plants is $100 billion being withheld from other critical social services.

What? No it isn't.

There are many places the government could use to appropriate funds, not just social services. The military, for example. Other subsidies. Tax credits. Simply increasing the debt.

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.