Are cryptocurrencies a threat to the dollar?
Personally, I do not think so?

You have understood about the cryptocurrencies wrong I think. You will find the cryptocurrencies against to banks not to the fiat cashes. Example if you own your bank there is no mediator to handle the money of yours.
Then these kind of scams been done by the banks on consumers will be reduced. Actually I support to bitcoin and alts more than banks. There is no scams between the crypto transactions.