ever heard of Monetery reforms?
thats when the national banking cartels messed up their money printing, and then introduced a new currency (named after the old one) but with a different value.
to continue power police, legislation, army, universities, schools.
imagine the usa does that, under trump, or not trump but the us kongress which is very likely.
then all bitcoin usd trade would have to be reviewed, as the old us dollar would be worthless fraction of the new us dollar
regards
What you are talking is essentially de-monetization and re-monetization process that recently happened in India on November 8th 2017. Notes of certain denomination became worthless just within a blink of an eye and common public were forced to stand in the queue to changes their notes to the new one. Obviously Black money holders could not exchange a major chunk of their money due to the deposit limit and lost almost everything.
However, that process didn't effect the bitcoin progress in my country, instead a lot of people indeed converted their money into cryptos to bypass this banking ban through various channels and shell companies.
Valuation of currency doesn't change after issuing a new denomination. US congress can't control the value of USD. The value of a currency depends on various factors like debt ratio, Foreign reserve etc. So monetary would not kill cryptos in any way, instead it will go stronger during that phase as more people would want to bypass that phase by converting their money into various other assets.