NASA needs a passion project on which they can fire on all cylinders and do something big.
No, the American people need a passion project for space. The space race happened because it was "Us vs Them" and when you got the people behind you, politics generally gets out of the way.
But when you don't have the people behind you, politics gets in the way and you end up with stuff like the Shuttle and people opposing you on purely ideological grounds.
Hell, try doing any pure science research, and it's heavily politicized.
The only way to do stuff like mine asteroids or go to Mars is to somehow light a fire that gets people excited enough to actually do it. And that generally takes an external threat. I mean, WWII is an example of how you can do into massive deficit spending and have everyone "suffer" (rationing, wage controls, etc) for the "greater good". Ditto the space race - can't let those Ruskies win, after all, so full speed ahead, damn everything else.
These days we're all engaged in piles of petty squabbles - science vs. religion, taxation, spending, climate change, conservation, oil, etc.