That's exactly what the authorities will do. In fact it'll be extraordinarily trivial for the G30 to regulate Monero et al. out of common use in larger markets if they want to. If you want to use it, you'll be a financial criminal, 99.9% of people in the G30 will avoid it accordingly.
It's not so simple. You only need one exchange, anywhere in the world, that will exchange Monero for non-banned cryptos, and the market will flow freely.
Except that any exchange trafficking in an illegal coin could be banned as well, and so your transactions with that exchange in other coins (in order to convert to or from Monero) would be traceable and illegal.
Are certain cryptographic algorithms going to be banned when used in a cryptocurrency?
These are all loopholes they'd have to tie up if they want to go down that rabbit hole. It will cost them millions of dollars and man hours to stop it. You're baiting the government to play a neverending and increasingly complex game of whack of a mole. It seems like a beyond awful use of tax dollars to me. We cannot let our government get sucked down the black hole of trying to regulate the unregulatable. They need to come up with solutions to co-exist with it, not outright ban it. That will be a disaster in the making on par with the war on drugs.
