How would the US have reacted if the USSR deployed nuclear weapons in Afghanistan?

I've seen the question posed here a few times what if the US had ever decided to use Nukes during the Vietnam war? However what if the Soviets during the Afghan war of the 80s deployed nukes, tactical or otherwise.

How would the US have reacted to this?
 
By dropping negotiations on/abrogating the INF treaty as well as organizing an international boycott of trade with the Soviet Bloc.
 
If your suggesting they actually use them, what would be the target? This was a counter insurgency war, that lacked high value targets that would justify the use of nukes. The political ramifications would be enormous. The United States, EU, China, Japan, and most of the rest of the world would be shocked. Tensions between the Soviets, NATO, and China would go off the chart, putting everyone on a hair trigger. The people living in the Warsaw Pact Countries might launch mass protests. The most severe sanctions would be imposed on a weakening Soviet Economy. In 1979 the West Germans told the Soviets if they invaded Poland it would mean the end of Detente. This would rise to the same level of escalation of force that would demand a response.
 
By dropping negotiations on/abrogating the INF treaty as well as organizing an international boycott of trade with the Soviet Bloc.
I suspect the partial nuclear test ban treaty would likely have collapsed as well and I suspect there would have been other consequences as well.
 
Seems to me like it'd be a major step towards lowering the threshold for future nuke usage, which would be a very bad thing for all concerned. Even the Soviets.
 
It's like US using nukes in Mexico to punish cartels. Requires quite a mad government. Not Brezhnev or other Kremlin gerontocrats.
 
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