'Tis but a mire of bad choices, PN, to be sure.
Can you keep the SSBNs (at sea) safe? Probably. Shore establishments / harbours / rearming facilities? Not so much...
However you wrap it up, it seems to me that the only utility of a 'second strike' ability is counter - value. There's no 'counter - force' left (or, likely, none that you have much in the way of resources left to locate). For that matter, the 'counter - value' element is probably moot too. Even if I choose not to target their cities or salt their lands (considerably and deliberately adding to the fallout quota in the process), most everyone left will soon succumb to radiation or (more likely for the larger number) hunger.
Decisions, decisions, eh?
With that in mind, and assuming much / some of the Southern hemisphere remains intact (relatively speaking) in this scenario, might one not wish to retain leverage in the negotiation which begins: 'Dear Argentina*, you will make sure we have the beef / grain that we need, won't you?'
Supremely distasteful, but dire exigencies demand dire provision.
Best,
Frank
*Other hostages may be available.
Last edited by JG54; 6th Feb 2016 at 00:17.
Reason: Addendum.