What would happen to Bitcoin’s value if all countries banned crypto exchanges together ? Can it survive such an action ?
This question would hold relevance many years ago when bitcoin was still very early especially when that mt gox hack happened and most recently, the FTX collapse. But since bitcoin didn't stop there, those events alone should be able to answer your questions.
Fwiw, even if exchanges are banned, there would be ton of decentralized solutions that would come into play.
AFAIK, FTX collapses had nothing to do with Bitcoin, it was panic and fear of the exchange not liquid that hurt the price, the exchange token was worth billions became nothing. When the FUD was subdue, the price came back afterwards. The Mt.gox incident was what I can recall that hurt Bitcoin price and trust of excajan because Bitcoin were stolen but there has been ongoing gradual distribution as there is approval of court before another batch transaction will take place.
If exchanges are banned, there is no room to panic or run away. All they have to do is to allow people withdraw their Bitcoin it's as simple as that. We will pivot everyone back to decentralized exchanges as it used to be but the question is, are countries that dumb to run away from free taxes? I don't think all countries are going to comply. Bitcoin isn't an illicit asset to call for the ban of exchanges except if the exchanges are supporting activities that are illegal.