lets say usa dollar and all currencies will be highly devalued .....then how we know the btc value??
most traders use USDT so if something happens with usa dollar is my USDT Will be worthless over night?
If USD will lose value then all local currencies of different countries will lose value too, I don't think that will happen. Our world is dependent on fiat. Imagine if it has no value, how are you going to buy things? How can you say this is cheap or not. You can't just say something cost 1btc without depending on a fiat currency.