Actually, if chess strength is judged by chess champions, the US was stronger than Russia in the 19th century.
Further, a quick look at Wikipedia shows that modern Chess as such did not really even exist in the 1700s. Modern Chess theory, based on position and piece value, originated in Europe and the United States in the late 19th century. Chess strength of any sort before that is irrelevant.
It's farcical to say that without modern chess theory you can't measure chess ability.
Russia had a strong reputation because strong players from other countries played against Russian players and lost. Have a look at Murray's A History of Chess (1913) it mentions a few accounts of Russia's strong chess abilities significantly pre-dating positional/piece value theory.
Further, a quick look at Wikipedia shows that modern Chess as such did not really even exist in the 1700s. Modern Chess theory, based on position and piece value, originated in Europe and the United States in the late 19th century. Chess strength of any sort before that is irrelevant.
So basically, the article is right.