If we take every dollar in existence and make the existing quantity of BTC equal that amount of value, what will a coin cost in the (now-defunct) dollar?
Just wondering what will happen if a large economy switch to Bitcoin
There's no such way, Bitcoin is decentralized and the dollar is centralized, I don't think that the well-developed country will do such a thing, they even have heavy regulations. Bitcoin needs also fiat to have a real value and I don't think it can overtake Bitcoin besides no one government replacing their fiat.
Yes, dollar being centralized can't be replaced by the decentralised bitcoin. Also, at any cost this isn't gonna happen. The low populated country El Salvador itself had opposition for considering bitcoin as legal tender. So, surely USA people will also have opposition. Bitcoin needs fiat to value it, which might change when direct acceptance increase.
I don't know even if this what IF will happen and what is the result to the economy, we know that the world's market influenced on the dollar value as of now.
The chances are no more considering the economic infrastructure and bitcoin. Maybe as an alternate to the USD we can see bitcoin getting used in the future as the generations are completely getting tied to technology.