What is the best way to see historic Bitcoin trading voumes (by value) by Country?
There is no way of finding that out.
Every single method has a lot of flaws.
The data from coindance comes only for localbitcoins and paxfull, many don't use those at all and the volume as a percentage of the global trade including centralized exchanges is just a drop in the ocean.
The locations of the exchange is again misleading, how do we count what's traded on Binance?
The currency pairs are also not a real source, you don't have to be a citizen of us to trade in $.
And more importantly, every single damn exchange is faking volumes big time to attract customers, especially the ones that focus on the country their reside in to claim the title of biggest exchange in x.
So, it's a quest that will lead to nowhere if you want accuracy.