You seem to forget that the USA has an outstanding credit rating with a perfect record. There is currently no concern about being able to pay off the debt if it is needed. The USA has one of the lowest tax rates and the biggest base of tax payers in the world. The debt could be paid off in full by increasing taxes a little (something that we are still unwilling to do, but it will have happen gradually after we get passed this mess)

One thing to always remember... There have been 20 recessions in the history of the USA, and every time it comes back stronger. Times have been worse in the past, with larger debts as a percentage of GDP and much larger wars.

Recessions are the best time to take on big projects, just look at history.