OK so that's the market cap of companies registered in each country that the site itself tracks, and I highly doubt all of them. The site lists 8545 companies worldwide which ie extremely low, and lists 3696 for the US and 17 in Russia. There are more than 17 companies in Russia. Russia has more than 1.2 billion USD worth of assets within it's jurisdiction.
Discussion
Oh yeah, I see your point. According to this page, it's number 91.
https://en.m.wikipedia.org/wiki/List_of_countries_by_stock_market_capitalization
That's a much better metric, but there's still a lot missing from it. That's only publicly traded companies, that doesn't account for all assets, both privately and publicly owned. Alaska's oil reserves, farmland, mineral deposits, existing factories, highway infrastructure. These are all examples of valuable assets that, while much of it is in the hands of publicly traded companies, most of it is not. Total valuation for a country is a hell of a lot more than just the valuation of it's stock market.