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?
Although it will be impossible, just to answer the question it is a yes.
USDT = USD
So it will also be valued as how USD will be.
But, I doubt it will be as low as it can get.
Just think about it, even now with the pandemic and the US being quite affected by high numbers of positive COVID-19 patients.
Their currency is still highly valued and strong. It's not that easy to preserve that.