I can’t decide if it’s worse to imply that Russians can’t learn English or to think that the anglosphere only exists in North America.
Other than that, there are no giveaway spellings or idioms. It could just as easily be someone whose exposure to English is dominated by technical documentation, which tends to use mostly American style.
I grew up in the US but lived most of my adult life abroad, and the only thing I can tell you for sure is that you should never stereotype anyone based on the way they use their second or third language.