It is an important point - here in Australia we don't have adequate onshore fuel reserves and we have only two or three remaining oil refineries, meaning the vast majority of our fuel is refined offshore and imported. This means basically our entire transport industry would fall over in (if I recall) around 20 days if our shipping was blockaded.

But I think you're wrong on one point - going green isn't an economic hit in the scheme of things - even not counting the possibly incredibly high costs of climate change into the future (food insecurity, more frequent and more severe weather disasters, etc.) - renewable generation is cheap, and storage is also getting cheaper every year. Energy efficiency improvements have also seen demand trending down even as populations increase and there is a push towards electrification. Meanwhile nuclear has always been pretty expensive, and coal and gas prices have been fairly high in recent years. With some demand management, more distributed storage, new battery technologies, economies of scale etc., the cost of highly renewable grids is not likely to be a big deal.