First, you have not previously pledged to your neighbors that you would not own firearms. North Korea has pledged to not own nukes. Second, you do not loudly threaten your neighbors' health and well-being. North Korea does.
Can anyone explain how testing something spells trouble.
In international relations, it's one thing to do "concealed carry" (for example, Israel or pre-1990 South Africa), but testing is akin to brandishing (witness how hot things got between India and Pakistan in the wake of their nuclear tests--it damn near turned into a nuclear war shortly after 9/11).
But it didn't and these countries were already shooting at each other.
I guess after NK tests the USA will send them more aid and tax dollars to make them not do it again.