I don't get why this line is repeated so much. Verbal agreements and reassurances in the realm of foreign policy are essentially worthless, especially when you're dealing with democratically elected leaders. Unless you have a formal agreement the next president or prime minister has to abide by, there is no continuity.

This expansion argument also ignores that Eastern European countries are joining NATO of their own accord.

Btw Russia and the US also signed the Budapest memorandum to respect Ukraine's sovereignty.