Trump's North Korea red line

[fred]

My question was...
What would the ramifications be?
What would the ramifications be if they do nothing?

Thanks for your insight thus far..
U.S is still the most powerful military nation on the planet...By far.

[Terpe]

My question was...
What would the ramifications be?

Most likely retaliations against South Korea and Japan.

What would the ramifications be if they do nothing?

Hmmm, tricky one really.
I can't imagine the option of US doing nothing.
I'd expect US to apply very strong sanctions against anyone seen to be assisting N Korea.
As that stands it would be companies in China

Not sure how China might respond to that....

Personally I hope Mr Trump has an ace up his sleeve