The last bomb they tested is like 10x more powerful than the little boy, but I'm pretty sure the trade winds would send fallout into china
castle bravo : 15,000 kt : biggest by us
the LGM-30 minuteman can fly for 8,100 miles, and with a W87/W88 warhead,
nk missile test in 2017 : 200-300 kt : biggest by nk
Hwasong-12 flew for 30 minutes. (no information about the warhead yield)
us would obliterate nk if we had a nuclear war
US stockpile > NK stockpile
stuff edit : hwasong-12 yield : no info about the type
hwasong is x2.6 times larger than little boy, 15 kt
castle bravo is 1,000x
w88 is 31.6x (but the w88 warheads would be in packs, inside the icbm so this is one warhead)