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.
RE: Why the current Monetary Policies mean Bitcoin wins either way