The reality tho is the fact that this coin and Crypto in general is backed by nothing but Fiat and this is why I always want to sell my BTC before it's to late (it been stolen but that beside the point)
Literally speaking, Bitcoin or cryptocurrency is not backed by nothing at all. It is backed by the demand of people. Cryptocurrency is a free market where every individual has the right to process a buy order which is called demand.
If Bitcoin or other cryptocurrency is backed by nothing at all then you can see its market price plummet to oblivion. It is not only backed by dollar but also backed by other currency due to the variety of market demands. Many people buy Bitcoin through different fiat and cryptocurrencies and it is obvious by the Bitcoin trading pairs.
To answer your title, if dollar collapsed, Bitcoin price value in relation to dollar will soar. The lower the value of the trading currency pair is, the higher the price of bitcoin in that currency.