Indian government (maybe other also) say that " to ban cryptocurrency we need global help" my question is : can bitcoin be banned if all government will agree to ban bitcoin
If governments could ban Bitcoin they would have done it a long time ago as they want now. They don't really want to ban bitcoin, but rather want to regulate.
If you mean the ban imposed by the government of India and the regulations starting to re-enforce
Cryptocurrency and Legal Digital Currency Bill Regulations 2021. So what exactly do they want to ban cryptocurrencies and create regulations. The answer is I think
"Project self launch digital eye" and most countries prohibit and make regulations just for this purpose. If you look further, almost all countries don't really ban cryptocurrencies, they just want to regulate and control them like fiat.
Some governments have already done that long time ago and some of them have also gone through several phases of unbanning and banning Bitcoin. Now the status of Bitcoin is that many countries or governments rather have embraced it. They have already proven that Bitcoin wasn't really a scam or bad but it can be an asset to help them and their country to improve.
Bitcoin being a decentralized crypto could mean that there is no way for any governments to regulate it and maybe that is the reason why they just banned it directly. Right now, governments do only come up with their own crypto which is called CBDC which they can regulate easily.