When America can afford to look to the stars, they should. Until then, they are wasting their time (and precious taxpayer money).
If that isn't the finest example of short-sighted thinking, I don't know what is. What you're suggesting is we wait until the last possible second to explore what might be out there just because NASA's budget represents a fraction of a percent of the overall national budget.
If you're that concerned about Federal spending, we can cut the military by 50%, stop all subsidies to business (sugar productoin, ethanol production, farm subsidies in general, scientific advances, production incentives, etc), not to mention all the entitlements people complain someone else is receiving but not the ones they're receiving.
If you want to go that way, I'll back you, but you can't then complain when things fall apart because the private sector has come to rely on government largess.