Hey, no harm done.  In the USA people like to say we are a democracy, but we really are more of a Socialistic Republic than anything.  And I don't mean that in a bad way - Fire, Police, Military, FAA, etc. are all socialistic elements of government.   And the USA is a democratic republic by it's own definition. 

Well, except when business is buying officials.  Then that’s generally a very bad thing and there are other words for that. 

But then technically Virginia is not a state, but a commonwealth and Louisiana has no counties.

So what would they call this new country?  The Democratic People's Republic of North America?  (or just DPRONA?)

Vietnam lost millions of people thanks to America trying and failing to contain "communism". Even so it still beat America despite losing 30 times as many people as it held out long enough and was willing to sacrifice themselves to be independent, which is what they wanted in the 50's when fighting the French. 

Guerillas used their environment to the best and used the superior technology of the invader against the invader if given the chance. If anything we could say nationalism was what won Vietnam. The thing with that war is that people at home in America were gradually losing interest in it and going against it, especially among the young. The fact that the media were allowed to report on every gruesome detail made support for it less likely. 

All i know is America certainly didn't win in Vietnam and hasn't learnt a lesson from it since. 

Back to topic, Mexico would probably still beat North Korea. Unless China got involved on North Korea's side...

Mexico has Machete, and this is what he'll do to that fat moron Kim Jong-Un   

Without anyone else interupting, NK should take it easily. Of cource, it's not like the US would let them take a country/defeat one at their doorstep, so Mexico would end up crushing them completely with the support of the US, and probably everyone else as well.

Edit: I'm not sure how modernized their army is though, but they should still be able to beat Mexico outside of Mexico.

The problem NK have is though they have a very large army, it isn't a very modern one and lots of their equipment is made up of stuff from China and the USSR from 20 or 30 years ago. Also Mexico is a far bigger country and has far more advanced armed forces, so I suspect the Mexicans would win, even if in terms of standing forces, they're outnumbered

EDIT: However, it seems NK are fully aware of this and have tailored their military to fight a highly mobile guerilla war, so it would be dependent on the circumstances of the war - a Mexican invasion of NK probably wouldn't go well. Basically they're closely matched, I don't know if either could 'win'

Mexico, cause it would not remain a two country war. Could start WW3 though

Sticking to the basic question which has nothing to do with the US, China or anyone else.

1) If NK invaded Mexico the Mexicans will kick them out.

2) If Mexico invaded NK then NK will win.

As it stands I seriously doubt any of these nations has the capability to launch an invasion on each other.

3) Nukes: If NK has enough nukes (or dirty bombs) that are capable of being delivered to Mexico and turn that country (or vast areas of it) into a radiation zone then there is only one winner. Again I doubt they have enough missiles and range to do this but with a country as secretive as NK who knows.

The US and China question: In this day and age can any nation with the status of Mexico and N.Korea go to war without bringing other countries into the conflict.?
Many years ago the British fought Argentina but as the US and many other western nations were relatively friendly with both, they did the best thing and stayed out of it.

True, but that was only over the Falklands, there was never any talk of the UK invading mainland Argentina which may have been different (personally I think most countries would've backed the British given that the USA and others made some gestures of support)

If Mexico was attacked I think the USA would support them due to the threat to the USA's borders and the fact they've taken the role of worldwide military policeman. If North Korea was attacked then I think China would just cut it loose - they would gain very little and personally, I don't think they have any appetite to intervene in foreign affairs in this way, even though they're perfectly capable of it

One interesting angle would be South Korea's reaction - they still lay claim to North Korea's territory, so having a foreign power occupy it rather than giving it to them would be rather awkward, but given they're USA allies I doubt that would happen

NK.

Not quite, North Korea's military first policy allows them to even eat North Korean civilians if need arises.