North Korea is still secretly building nuclear weapons even though it’s dismantled one of it’s biggest nuclear weapons facilities. This facility is the Punggye-ri Nuclear Test Site (which was dismantled in April 2018 in an effort to reach out to America).

Sadly, A few months later, and after the Trump-Kim Summit, it was reported that North Korea was making more nuclear weapons in other smaller and more remote secret facilities.
And the most recent meeting with Trump and Kim showed the Donald walking out of the meeting as North Korea and America couldn’t get to terms with sanctions, the most prominent of them all is that North Korea, apparently, won’t give up it’s nukes.
One problem of America is that, in order to get economic aid, the nation must fall under the complete control of America and it’s wishes. IF one of those demands isn’t met, there can’t be a deal. And nuclear weapons has ‘Merica spooked.
America has not attacked any state that has nuclear weapons. Israel. Russia. South Africa (formerly), China, France, United Kingdom, India, Pakistan (sort of) and North Korea and many others.
And as such, America wants a sort of insurance policy or leverage against a nation it wants to do it’s bidding and trading with.
However, in light of the apparent reaching out of North Korea to seek some measure of peace, the military drills and operations in the joint US-South Korean side will be reduced significantly in an effort to maintain such an advancement.
In fact, the joint operations center already suspended some key military drills in an effort to make the two Koreas come closer to peace.
Despite Trump walking out on the meeting, however, the United States and North Korea (technically still at war) are open to more talks in the future.
Reference: Trump says N. Korea has no economic future if it has nuclear weapons