It could simply mean that running space programs in the USA is far more costly than in other countries. Someone did say that NASA of the recent age is less about research and more about massive employment.

I would say, the price difference adjusted budget of NASA is also much bigger than that of any other nation. Do you see the Russians walking on the moon or driving nuclear cars on Mars?

Guess this is because no other country has that level of expertise of space program like US.

Your causality presumption may be reversed.