With something like 45% of processing controlled by entities in Iran, China, and Russia, it seems like an absolute fools game to put any significant wealth in Bitcoin. All it would take is a significantly effective worm to destroy bitcoin. But hypers gonna hype.
You couldn't pay me to hold a Bitcoin.
Since Bitcoin is software anyone can fork it and create a currency y with the same ledger up to the fork but few people do because convincing other people to trade for it without a very strong argument is hard.
Or just announce and prove that they are doing it, thereby causing a run on bitcoin and all the other bozobucks.
As opposed to any other modern financial system with significant liquidity in digital assets?
I fail to see how substantial private ownership distributed amongst those countries makes it significantly vulnerable.
Software versions and updates require social / economic consensus and have nothing to do with mining power. Bitcoin is open-source protocol / software and everyone can use whichever version they like. But there's also economic incentives to use the most used version and to make sure that it will keep being the most used version, i.e. forks are bad and should be avoided, therefore it's in everyone's interest to reach consensus.