There is an interesting discussion of Russian Social Security at

https://www.castroandco.com/blog/2019/december/u-s-tax-treatment-of-russian-social-individual-I/

The author states:

Code section 6114 requires any person relying on a tax treaty to disclose such position on his or her federal income tax return unless an exception applies. IRS Form 8833 is used to make a disclosure regarding a treaty-based return position. A separate form is required for each treaty-based return position taken by the taxpayer.