McAffee moved his mining operations to China, 'cause he gets his electricity there for free. There are also some mining operations in Iceland with an electricity rate of 0,05 cents per kWh. If your city want to compete with that, I suggest a rate of zero to join the club. But then you might just want to run the mining business on your own.

Lets assume the US government wants to ban BTC. The supreme court already ruled, that software of any kind is protected by the 1st amendment. There are nine categories, which are not considered 'free speech" ( http://www.newseuminstitute.org/about/faq/which-types-of-speech-are-not-protected-by-the-first-amendment/ )

In conclusion: Transfereing BTC from one wallet to another can not be banned under current US law. There are also technically problems to ban BTC. The wallets are anonymous (if you cloak your IP/dial-in via anon-service) so in order to ban BTC, the US government has to detach themselves from the internet, build an own national intra-net and ban anon-service. That way, they can see who is using BTC and prosecute the users of it.
That will never happen, if you ask me. What the government actually can do is banning BTC from the exchanges so that you can't trade BTC into fiat currencies. That is all they can do, as far as I'm concern. But of course they can pull something illegal. Executive Order 6102 is considered unconstitutional today, it forbid US citizen and foreigners to own gold from 1933 to 1974. So this might happen again in the future.

Selling BTC for PayPal, that can be charged back after ... month, sounds like a bead idea.

With BTC as legal tender, you'll need no income tax. There was no income tax on US citizen, before the FED act.

Technically a BTC isn't a token. There was no ICO to crowdfund that technology. The initial cost of a BTC was 'undetermined'

If all governments of the world causes a global power outage and are the only ones that can run the blockchain on a (secret) computer, they can alter the block and the code, literally destroying the currency.

Beside that, there are some scenarios what can cause BTC to go down to zero in value:
1) The next 'new thing' that makes BTC obsolete, so ppl are flipping to the new technology. That can be ... OPEC is setting up an alt-coin and accepting only these crypto currency as a payment for crude oil. I think we will see a huge dip in all cryptos then.
2) When ppl agree on each other that BTC are worthless. But keep in mind that BTC can rise from 0.00 to even $5k, when ppl agree that one BTC is worth $5k again like between 2010 and 2017.
3) someone successfully hacks all existing nodes in the network simultaneously (very unlikely)
4) The day the last users of BTC losing their keys for their wallets and there are simply no more BTC in circulation (after the last BTC had already be mined)
5) A zombie apocalypse, judgement day, a global killer comet a.s.o.

We will find out soon. There is a rumor that JPM sold BTC short in June/July to bring the price down. Some say they have a buy option at $2500. If you look at the chart, BTC went down from $2,800 to $1,700. JPM might have known that China was about to close exchanges and speculated that BTC would've taken a severe dip.
But what happened (assuming the rumor is true)... the market just soaked in all the BTC like a sponge. After the short sale ended, BTC rose to a new $5k high. And now it's back to $4k after the market soaked up the BTC from the Chinese exchanges. In that case: Yes, the downward movements would be artificial, it would be explain why miners like Genesis aren't paying out BTC, because JPM is most likely to have 'em lend by big miners. It might be even possible that Mcafee lend them too and why there was a $16M BTC transfer between two wallets w/o cashing them in prior to June.

Now, I don't know if these rumors are correct or just imagination, but the future will tell. If JPM thought they could 'destroy' the trust in BTC by selling them short just a month before China was announcing to close exchanges and giving them back at a waaaay lower price, BTC will go up a lot, depending on how much BTC JPM has to buy back... or the insurance company that gave them a $2,500 per BTC buy option.