Most leaders' primary focus is on retaining control within their own society. Presumably Kim Jong Un is the same.
I think that the premise "he said he will attack, he will look like a pansy at home for not attacking" is flawed on several levels:
1. North Korea's top leader has made such threats for decades, it didn't hurt them before.
2. He's threatening the biggest kid on the block, that looks strong even if he doesn't do it.
3. He says anything to Uncle Sam, Uncle Sam is too chicken to respond. Big Daddy Kim must be Big Man!
4. As his weaponry increases while threats remain similar to the past, he overall appears stronger than before rather than weaker.
5. He can always offer an excuse for not attacking at this moment. Tomorrow's another day.
His threats against the US unite his people against an enemy, create an atmosphere of crisis requiring obedience, and fulfill the Kim family's strategy of sounding like strong leaders. All of these support the agenda of controlling his own people and subordinates.
What's new isn't the threats, it's the missile range. Threats and such, including the possibility of attacking US allies/interests, have been constant for decades from North Korea, with periodic variance in the wild words. Nothing changed since I read a book chapter on topic 10 years ago when his Dad was in power. The book's topic was basically "flash points of Asia, and how Asian conflicts will drive history in the next 10 years." (Title was "Rivals: How the Power Struggle Between China, India and Japan Will Shape Our Next Decade", copyright 2008.) All regional news developments since then (Asian space race, Chinese islands, Japan vs China re Yasukuni shrine, Kim Jong Un takes over for his Dad) were discussed as likely or possible then, excepting Duterte. Fwiw, events have been calmer than predictions if anything. The only slight surprise was Kim Jong Un himself - the author believed that it was unclear which child would rule.
TL;DR - This has been simmering for ages. It probably won't boil over now either.