sure, to pay this month. probably the only thing that would save the mortgages would be for the government to undertake to pay them, or a portion of them, if the original homeowners couldn't.

even ignoring administrative costs, i suspect that would cost orders of magnitude more than buying the securities from the bank for pennies on the dollar. then when you add administrative costs on top of that...

i suspect the answer to your question is that no one in the financial sector could possibly believe that the u.s. government could afford to do what you're suggesting even given that it can print money.