"Soft power" of American power will definitely decline. Particularly that part that is drawn from the positive example of life quality of it's citizens. There will still be "lead by example" in less benign form - that will survive better. And raw military power will go away last.
So, sure - I don't expect the US to become completely impotent tomorrow. However, it will be less powerful in that way in which I would like it to be powerful and it may be more powerful in the way I would hate. Pretty much be more like Russia instead of being less like Russia.
Economic usefulness of American space program is not that great either. Particularly, when you will notice that the US doesn't pay for it's space program using taxes - it pays for this program by running huge deficits. So, its really a question where is the balance in this program. At best, it is partially recovering money that are spent on military anyway.