Upvote:7
Even if you had to disclose your US citizenship (which you don't), it won't make you ineligible for visa-free entry with your other passport. Why would it?
Citizenship is not a taint, as in, you are "tainted" with US citizenship and therefore require a visa. Citizenship is a grant, as in, if you're granted "some country" citizenship you don't require a visa.
I know that some Middle Eastern states see citizenship as a taint vs. Israel, but this is not the case generally and this isn't the case with Russia.