That's a nice thought experiment. Let's start with the powers of the US President, though. I realize that Wikipedia is not among the most reliable sources, but I find it fairly accurate is such formal matters.
The Constitution explicitly assigns the president the power to sign or veto legislation, command the armed forces, ask for the written opinion of their Cabinet, convene or adjourn Congress, grant reprieves and pardons, and receive ambassadors. The president oversees federal law execution by directing and removing executive officers. The president may make treaties, which need to be ratified by two-thirds of the Senate, and is accorded those foreign-affairs functions not otherwise granted to Congress or shared with the Senate. Thus, the president can control the formation and communication of foreign policy and can direct the nation's diplomatic corps. The president may also appoint Article III judges and some officers with the advice and consent of the U.S. Senate. In the condition of a Senate recess, the president may make a temporary appointment.
Just as I suspected (because it's similar in my country), the President cannot intervene in economic matters. It seems that executive orders should be dedicated to important governmental priorities, so I am not sure that pulling this stuff with cryptos off is even possible. However, since thought experiments usually require us to accept the initial conditions, let's assume it's possible, and Trump does that. It's known that there are quite a lot of Bitcoin users that come from the US, but it's hard to determine how many. I think it would affect the price in a negative way, leading to a 20% drop or so, but eventually, Bitcoin would recover.
The president can intervene in economic matters. Gold was banned for a bit in the USA. Trump can by executive order to tariffs.
So he could 'ban bitcoin' on national security issues rather than economic to get around this.
Again, all this is unlikely and could be challenged in court, but lately, anything is possible in the USA if legit refugees are being separated with their children and kept indefinitely apart.
There is a wide world of silliness under Trump, so I'm sure, he could try to ban bitcoin on a whim, depends on how folk take such a threat. Either he'd be laughed at or in the short
term ignored or he could get away with dumping the price down to 100 USD and drive institutional investors away.
The way the world is lately in denial in the USA with electing trump and denial of climate change etc, no idea...its all beyond the scope of me trying to keep track of.
utterly befuddled
brad