The US deficit is caused by the Bush tax cuts, which is part of the overall conservative strategy to redistribute income upward. The tax cuts do raise demand, but you could get bigger bang for the buck in other ways if that was your first priority.

I think the explosion in consumer debt is an attempt by households to maintain living standards in the face of incomes that are growing only slowly, or even shrinking in real terms. This does prop up demand, but it is not sustainable in the long run. Again, the root of the problem is political: slow wage and income growth, due to excessive corporate power brought about by the evisceration of institutions like labor unions and labor market regulations designed to ensure that workers get their fair share of the growing pie.