My understanding is that most of the mining is currently done in China and Iceland because China offered very cheap or even free electricity to stimulate industry and Iceland has access to so much 'free' geothermal electricity. China's version is hugely polluting and powered by coal and nuclear sources.
It is massively important that all computing technology is made more efficient and that is an ongoing process behind the scenes at all levels (usually). In the case of Bitcoin, my understanding is that it is quite inefficient in terms of the resources needed to mine it and there are much more efficient cryptocurrnencies from the perspective of resource usage, but I have never seen a comparison that shows how they all stack up against each other - it would be interesting to research.
Some great points .... it is also cold in Iceland and so they don't need as much electricity to power the fans to keep the kit cool. They just have a warehouses with a cold through draught I believe!