What if either India or China cease to exist?

There are many movies on what happens a city in US get wiped out, and I am sure that is already is sated subject but there are unsatisfied viewers.

More worrying this if there is a natural disaster in either India or China, big enough to wipe the country out of the map, world would have have serious problems. The disaster that I am thinking is something like some celestial object hitting those country or great Everest bursting out. In such a scenario following are the things to worry...

a) What happens to world's economic balance. Currently China is world's biggest factory and we are all have been made dependent on it?

b) Will UN secure the borders of affected country against vicious neighbors? Take an scenario where India gets wiped out of the planet earth, and then expatriate Indians would like to rebuild the country, will the UN help them secure the nation against China/Pakistan?

I think Hollywood should make a movie on this subject.

Do we need Natural disasters?

In one word I would say "YES". It has advantages, one is that it reminds humans that they are not the masters and that might make them behave little bit decently. If were no natural disasters, I am sure humans would have pruned the nature completely.

There is another tiny advantage of bringing the population down, but I am yet to see the result of this because people who dies in these accidents are usually in terms on 1000s++ which is nothing compared to billions++ population. Also if you take in to account the money that goes in to reinstate the affected people, it is not worth.

Needless to say that people affected from it this is insensitive, but in broader terms these these catastrophes should make us more responsible.