The article wasn't dropped - it is correctly non-present. The general concept at play here is sometimes called "zero article" or "zero marking." The sentence would sound very strange to me if it had an article. Similarly, "Can we say we can call it the English grammar...." should not have an article.
It is not about it being abstract or not. Abstract nouns often take articles ("A love like the love that they shared is a thing of beauty.") Conversely, concrete nouns sometimes take no article. (For instance, your last sentence, I guess it is happening without being paid due attention by the native speakers. Should be I guess it is happening without being paid due attention by native speakers )
Zero article is common for both plural and uncountable nouns.:
Do you like meat?
Meat is uncountable, not plural, and I am asking about the general class of things which could be considered to be meat.
I feel pain in my left leg.
Pain is uncountable.
I train chickens.
Chickens is plural.
Godzilla threatens world peace
World peace is uncountable.
Back to your original quote:
"I think that China is genuinely worried about the threat, Kim Jung Un, and his nuclear programs poses to the penninsula and to international peace security.
You misheard it slightly, but in ways that change meaning. The transcript below the sound file gets it right:
I think China's genuinely worried about the threat that Kim Jong-un and his nuclear weapons program poses to the peninsula and to international peace and security.
International peace and security is being used to refer to two general ideas, not a specific episode of peace, or a detente between two countries, so it correctly does not have an article. Contrast with:
The peace and stability of Northeast Asia depends on the ability of South Korea, Japan and the United States to cooperate effectively to meet whatever challenges Pyongyang may pose.
(From National Interest
Here there is a specific peace in a specific reason that is being discussed, so the direct article is appropriate.
February 3, 1959 was an important day in history.
History is a general uncountable idea
February 3, 1959 was an important day in the history of rock and roll
Now we have a specific little subset of history.