THIS IS A GOOD QUESTION
Um. I don’t think any particular company’s disappearance will have ANY material impact on the world. It’s true for example, that if we lost Google, the world would feel it rapidly and severely. Google simply supplies too many services and too many of them for free, and that would be a problem. But it’s possible to simply nationalize the service and restore it. For all intents and purposes google is now a piece of national infrastructure as important as the phone networks, and rail lines.
If any large company that manages communications today went offline – the major carriers, the competitors would easily take over operations. If any oil company. The same. Pretty much all of them are not unique.
I think if Microsoft disappeared overnight that would cause a lot of disruption to the world over a few years, but I think it would lead to innovation and profitability.
I think if Apple disappeared it would trash the american stock market.
I think that if one of the too-big-to-fail banks in the west caused a cascade failure of other too-big-to-fail banks, that would cause a catastrophe to the world, and this has been the subject of both fictional, political, economic, and even military analysis. At this point cutting a country out of the world banking system is very nearly as serious as nuclear warfare, which is what brought Russia under control in 2014.
The biggest ‘companies’ of all are governments, and the collapse of a major G7 government would … well that would be very, very, bad.