If you own bitcoin you don't even own a line of code. You own a number, that's it.

The Internet and mining won't go down across the world either. There are renewable solutions in Asia and Europe that'd probably be capable of taking over. 50% of power in Europe has to come from renewables, its not as far to get it up to 100% as you might think especially if technology and efficiency improves. And if the Internet goes down for good, we'll probably end up with communism while we work out what to do about it.