Actually, the US is Ctrl+P-ing now. That's what QE is all about: from the perspective of the private sector, QE is equivalent to the government creating money out of thin air to pay back the debt. This is only obfuscated a bit by the fact that treasury and central bank have separate balances.

Why borrow when you can print?

My guess is a combination of (a) most people are afraid of change (case in point: you), (b) the people owning treasury bonds effectively get a hidden subsidy via the interest paid by government, and (c) the problem is framed in such a way that most people never even question the existing institutional arrangement - and when they do, they tend to do it in terribly uninformed ways.

No such thing as risk-free debt.

Please explain under which conditions the US government would become unable to fulfill the promises implied by its debt.