According to this report by the Bullitin of the Atomic Scientists, the US maintains an inventory of approximately 500 “non-strategic” nuclear warheads plus 790 in reserve. Most boosted fission devices (including the boosted fission primaries of thermonuclear devices) have had their tritium reservoirs removed because of decay; the ability to refurbish this fuel is uncertain, particularly given the expense of commercial tritium and the de facto shutdown of government nuclear production facilities. In addition, there is increasing concern regarding the aging and survellience of the plutonium and enriched uranium shells; while the amount of lost material is very small, the structural effects, particularly microfine fractures resulting from alpha production might impact detonation efficiency. Since we can no longer perform physical testing, computer simulation is done to predict the effect, but without testing to correlate, it’s all pretty speculative at this point.
The use of Mutually Assured Destruction (MAD) is no longer in use as a SIOP, lacking a single strategic enemy as the focus, nor does it rely upon the singluar use of “big megaton multiwarhead ubermissiles”; the MMIII MIRV carried the W62, W78, and W87 warheads at yields of about 170, 350, and 300-475 kT, respectively. The MX/Peacekeeper carried the W87, and the Trident C4/D5 carried the W76 (100kT) and various configurations of the W88 (variable yield up to an estimated 475kT). The Titan II missile did carry the W53 warhead (est. yield 9 MT) in a strategic/silo-killer roll, but was phased out of service in the mid-Eighties and never made up a majority of deployed boosters. So multi-megaton weapons are not an intrinsic part of the MAD philosophy.
What is a part of the strategy is an overwhelming force (countered by an equally overwhelming force) in which neither player can extract anything but a catastropic conclusion, a metaphorical Pyhrric victory, and the realization of this result by both (or all) participants. It’s questionable that this strategy was ever a realistic mapping of relations between superpowers–the theory relies on a large number of assumptions, lacking any one of which results in easily verified falsification by elementary game theory–an in the context of modern international events with several nuclear powers of varying degrees of capability, aggressiveness, and basic rationality, no longer applies.
Regarding the OP; this wouldn’t merely be a blunder, but an absolute bloody nightmare for the United States. The US has, if but tenuously, held the moral high road with regard to nuclear weapons with the claim (mostly true) that we will not plan to engage in unilateral use of nuclear weapons after WWII. Giving that up for some absolutely idiotic and unjustifiable action against insurgents by demolishing a city–regardless of what efforts we make to evacuate the citizens–would result in the US having zero credence with any legitimate nation or regime. Nor is there any expectation of a positive result for doing so; we’ve long squandered the goodwill from our own wounds by the attacks in 2001, and we’d earn universal condemnation for our actions should we even consider something like this.
Further light reading: CRS Report For Congress on Nonstrategic Nuclear Weapons [PDF].
Your line of reasoning is doubtful at best. The Red Army was in no position to advance beyond what became the Iron Curtain immediately after WWII, and while Western Europe rebuilt and became an economic force in and of itself, the Soviet Union and the satellite nations of the Warsaw Pact became increasingly backward and unstable, often proped up economically by Moscow. Nukes or no, it seems unlikely (in retrospect, though certainly not at the time) that the Soviet Union would have made serious inroads in Western Europe in the post-WWII environment. A more tenable hypothesis that the posession of nuclear weapons and the conflict between the USSR and the US-backed NATO alliance gave far more credence and legitimacy to the Soviet Union as a superpower than it would have had otherwise. Without their early production of nuclear weapons they’d have been a second-rate (though still major) power like China or France. The Soviets may have had a numerical advantage, but they lacked the logistical and economic capability to project and extend control, only winning the East Bloc states due to their German-occupied weakened condition (often postulated as being a critical factor in the timing of the Soviets breaking the Molotov-Ribbentrop Pact).
Stranger