is there some threat of the americans using low level nuclear weapons?

well, i'll remind you that they used depleted uranium in iraq and afghanistan which is equivalent or worse in terms of the radiation - and intentionally so. the radiation from an h-bomb is a secondary effect. with depleted uranium, you're dropping the birth defects on purpose - like agent orange.

but, it's worth pointing out that the conventional weapons they used in afghanistan were actually in the same power level as a small scale atomic weapon, so the difference between conventional and nuclear is not as profound as is generally imagined. it's really not as big a deal as you're imagining it is.