Every one in a while they rattle their sabers and launch a missile at or over Japan. None of them have ever contained a nuke; they've just been rocket demonstrations. Most have landed in the Sea of Japan, between North Korea and Japan, either intentionally or unintentionally. A couple have landed within Japan's territorial waters. Several have landed short of their projected landing zone due to mechanical failure. None have had warheads, and none have actually made landfall in Japan which would be, as you have correctly observed, an immediate shitstorm for N. Korea.

As of 2019 they have the capability to build ballistic missiles with the theoretical range to hit the western US, however I am not enough of an expert to determine if their rickety shit-rockets would be reliable enough to actually survive the journey or land accurately. If they actually did put a nuke on one, it wouldn't really matter much.

In 2018 and before, however, it was unlikely they had the capability yet to actually hit us.