The average interest rate on the debt is 2.43$, we have around $17 trillion debt, and you're talking about a $17 billion paydown (0.1%).
The amount of interest saved would be around $400 million per year. The profit on the GM bailout was $2400 million, so it would have taken 6 years for the decreased interest to total 2.4 billion.
>we can point at the various Solyndras the USA has bet on and lost while we are at it.
Can you point to the value of the hundreds or thousands of engineers and employees of failed new energy startups that received invaluable real world training and experience who are lending those talents to other companies.
Think about NASA and the 18 billion we "piss away" down that black hole every year, and the huge benefits that we derive from their work and the experience that those who work there gain.
Not every investment the government makes has a return in next-year-dollars.