You underestimate how resilient and effective people can be when needed. Yes, as mentioned earlier, it'd suck for a while, but we'd come up with solutions pretty quickly, as the entire country would rely on that.

Pretty much exactly a year ago, I was about leave home to go buy something, when the power was cut, garage door didn't open. Fine, jump into a taxi, and both of us notice that seemingly the entire town is without power. Once we arrive at the store in another town, same thing.

Turns out, the entire country had lost power, and would be without power for pretty much the rest of the day, and same thing in neigboring Portugal. We were literally without power, internet and cell-phone service for pretty much the entire day.

Did the entire of society pretty much was put on hold for a day? Yeah, but still we managed to go on with our day. I owed the taxi driver until the next time I saw him, the store accepted the same thing so we could buy some stuff, they noted down everything on paper, and so on.

We did survive, and thanks to humans being humans, we all could pretty much survive even that day.

Loosing Microsoft/Google/AWS would indeed be pretty much on a smaller scale, mostly impacting IT and everything related to IT, which is large swaths, but just like every other problem, it'll be worked around both temporarily and permanently, it's just in human nature to do.

Again, I'm not saying it wouldn't suck, nor that it wouldn't be difficult, but also, it wouldn't take a year before emails are being sent between companies again either.