No, the United States should not default on its debt, because it should be willing to make hard choices and live within its means, just like anyone else has to. If the United States keeps spending and then defaults, it will not be credible, and no one will want to lend it money or do business with it in the future.
The US government made many deals in order to secure the money in the first place, and so should be held to that. The US financial system has made itself integral to the financial system of the world, and the military it funds is often called upon to police the world. So defaulting, and having to rein in the US military would risk a world at war. That possibility seems too terrible to accept a default, and instead austerity measures make sense to pay our debts and scale back our great country.