Not really.
A lot of countries are openly supportive to it. If they all come together and try to ban it, or individually try to do so, it will always lead to debates. They don't want to risk that and shoot themselves in the foot.
The reality is that the banking industry has become a part of the tech industry and as tech evolves, new forms of currencies are bound to evolve. It is bound to become obsolete, so Bitcoin wins.
While I do think you are most likely correct, I don't think it means that it isn't a possibility. It may not be a strong possibility, but it still is one. To be honest, if the US and Donald Trump made it illegal to own or transact in bitcoin tomorrow, it would do a ton of damage, not kill it of course, but it would crash the price to levels not seen in years... and all it would take is a couple other big countries doing the same and bitcoin would be relegated to the underground as a niche currency probably never again reaching the valuations it's currently trading at today.
See. Not being a fan lead to discussions. What will a ban do?
There are a lot of people who have put in their money in cryptocurrencies though they don't understand it. They will also ask questions if they lose their money. In doing so, will have to understand more about everything and that includes the banking system.
It would do a ton of damage to Bitcoin? IDK, but it would most certainly do a ton of damage to the banking industry. Meet any american and ask about his life. He or She will tell you how many credit card payments he or she has to make. Why do they have so much debt?
People in America anyway hate the banking system, especially, since 2008 crashdown. If everybody starts asking questions, that will be a nightmare & that's what's going to happen if they try to ban it completely.
If they could do it, they would've done it. Why haven't they done it?
It hasn't been a real threat to the supremacy of the USD, at least not yet. If it gets to the point that it is, they will try to ban it. Bitcoin needs to keep itself in the digital gold category. As soon as it starts threatening the dollar, it will face a ton of backlash.
USD Supremacy
It's threatening the USD since the moment it came into existence. I agree, Bitcoin is the largest network and it is cryptogold.
USD is used for most of the global trade. However, does Bitcoin really need to threaten it that way?
I don't think so.
Co-existence
Both fiat and cryptos can work perfectly side by side and I think that's best. Those who want to take control of their money, they can do so by keeping their keys secure. Those who want to continue using the banking system, can continue doing so. Those want to use both the options, can do that as well.
For Bitcoin to be successful, banks don't have to go out of business. As far as Supremacy is concerned, USD will stay the way it is, but Bitcoin is a permissionless network.
Nobody is asking for Trump's permission here. If someone owns the keys and the network continues to exist, what will banning do? Nothing.. but lead to discussions. Banning will work as free advertisement for it.
Ban Blockchain Technology
Are they going to ban the Blockchain technology itself? It's powering new technologies and industries. The nation that bans it, will simply suffer losses and that will be a threat to the supremacy of USD.
Nitpick Certain Cryptocurrencies
So, will they nitpick a certain set of cryptos? How and what kind of laws will need to be passed? What will be the basis of filter? Again, it leads to discussions that lead to how these acts came into place and it becomes a threat to the banking industry itself. A lot of things they did in the past were illegal. Also, law works at its own pace and technology develops a lot faster.
Centralized Blockchains
Moreover, they cannot even think of going into that direction and so they are trying to cut away the decentralized aspect and adopt the Blockchain in every sphere. It is a powerful technology in itself and currency, centralized as well as decentralized is just one of the applications.
So, new sort of blockchain businesses emerging that want to keep the decentralized aspect out. Some are openly centralized and some try to look decentralized at the surface. Remember, Tron's takeover of Steem.