I remember that when N Korea a couple of years ago was stalling on agreements as they have done for the last 15 years, that the US suggested a change to Japan’s constitution and start thinking of building up defenses and nuclear arsenal.

See Wikipedia about changes after N Korea 1993 missile launch:

Following an increase in tensions with North Korea following the 1993 test of the Nodong-1 missile and the 1998 test of the Taepodong-1 missile over northern Japan, the JMSDF has also stepped up its role in theatre air defense of Japan. A ship-based anti-ballistic missile system was successfully test-fired on December 18, 2007 and has been installed on Japan’s Aegis-class destroyers. The JMSDF has also been active in preventing North Korean infiltrators from reaching Japan engaging and sinking a North Korean spyship in 2001. End of wikipedia entry

Japan has ABM probably a THADD system. But no offensive nuclear missiles. Japan could make viable nukes probably in months since they have the techinical know how and can be mated to US missiles. But Japan does not want the added risk of being a nuclear power.

N. Korea is not a real threat to the US . It is measurably more difficult to launch truly ballistic missiles tthat have long ranges. Only China, Russsia, US, France have that ability. Other nations have shortrange capabilities. Nukes are not that difficult the tech has been around for a long time. The missiles are not easy. China would not have had the ability if the US had not been seduced by greed and cheap satellitie launchs and Hughes and US companies gave the tech knowledge and assistance under Clinton. Then the stole all our nuclear reasearch.
Iranian launches are more failures than sucesses and so are N Korea launches. Nucke also take a lot of maintenance nad failures and fizszles occur if not properly maintained. I doubt that N Korea misssiles are maintained that well. Even US has gotten sloppy. The Russians may have more failures than anticipated.
Strategic reaccessment is needed and greater priority to Russian threats are needed. Especially if we have promised more than can be delivered to the Near Russian countries. I believe moving bases from western Europe into Poland and other Easter Euope countries are a good idea. This will increase Ruissia’s paranoia but if we really try we can out produce Rusia economically. And they will not be able to compete in military spending. The new capitalist countries with proper structure can create wealth and spend a lot on military equipment and training.
Azeribaijan and Georgia are strategic importance to both Russia and the US. We should definitely strive to acquire both as allies. So we need to get creative on solving the Armenian problem.
If we are able to demolish Iran nuclear ambitions and do a coup overturning the religious tryanny. Iran is very much afraid of the Shah’s son who has legitimate claims. A good ruler and western ally would soilidy the oil strtegic Azeribaijan.
We need to encourage India to solve its muslim terrorism problem and get them to counter Pakistan and we can take a page from Russia’s book and encourage India to push for Kashmir.
Pakistan will have to be contained in the future.
The largest future threat is China, to both Russia and the US. The US because we control the Pacific and they want hedgemony over that area. That means greater navy for the US.