In theory, the Government can shutdown bitcoin if all countries on this planet earth decide to shutdown bitcoin but the people are smart so I don't think this gonna be happening.
Next question what happens when bitcoin shuts down if all happen at once maybe the market will crash but not go to zero since most of the money is still on the chain and then people cant move their coin. the altcoin might will be hit hard and me as well
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Good luck with that. If governments around the world can't reach a common agreement, what makes you think all of them will unite against Bitcoin? As long as there's one country supporting the cryptocurrency, don't expect it to die anytime soon. Besides, there's nothing stopping people from secretly running BTC nodes. The code is open source too, allowing BTC to be developed/improved without restrictions.
With how big the Bitcoin blockchain is, I'd say governments are already too late to stop it. Their best bet would be to restrict people from buying/selling BTC across centralized exchanges. But that won't stop them from using other methods (DEX, P2P exchange). Ultimately, BTC will live alongside Fiat currencies for generations. As long as it stays decentralized, we should have nothing to worry about.