Can you substantiate this? Please provide to specific examples.
The first and most obvious is this: https://nsarchive.gwu.edu/briefing-book/russia-programs/2017...
Then comes the withdrawal from various nuclear treaties, the first being this: https://carnegieendowment.org/2021/12/13/u.s.-exit-from-anti...
GWB's attempted placement of a missile shield in Poland (ostensibly to defend from Iran) really heated the waters, although Obama ultimately killed it: https://en.wikipedia.org/wiki/United_States_missile_defense_...
Then Minsk failed, and Merkel, Hollande and Poroshenko's statements haven't helped at all. Merkel's is probably most important (Die Zeit has a paywall, so here is a PDF of the article): https://pdfhost.io/v/e0FRLvfzB_Angela_Merkel___Hatten_Sie_ge...
Most recently for the Russians is probably the seizing of their central bank's assets by the US and EU. I'm not sure how solid the legal rationale at the time was, but either way it happened: https://www.nytimes.com/2022/02/28/us/politics/us-sanctions-...
Neither side trusts the other. At all. So ultimately guns and blood will determine the result.
If Russia thinks a verbal assurance from the US SecState to a different country can bind NATO thirty years later as if it were a treaty, they're hopelessly naive. (They're not, of course. They know this is bullshit.)
Regardless of whether you think the Russians were hopelessly naive or full of shit, it is a promise broken. Remember, we're talking about negotiations, so their opinion matters too, regardless what you or I think about it.
None of which are empowered to individually and formally bind NATO to anything, let alone privately and verbally, and each to the Soviet Union, which hasn't existed for thirty years. "We're not gonna fuck with you while you're collapsing" was entirely reasonable and intentionally deescalatory at the time; pretending it's somehow a promise not to do anything while Russia moves into Georgia and Ukraine is silly.
The Budapest Memorandum, meanwhile, is an actual signed agreement by Russia.
Nope. It's a PR meme created for 2007 Munich Security Conference where Putin made his famous speech and needes justifications for imperialistic ambitions. Stunning economic growth before 2008 crisis allowed him to build up an army, and there he declared his vision. Nobody talked about such assurance before ca 2006-2007, and the 1997 founding act on mutual relations between NATO and Russia excplicitly says that signatories must "respect for sovereignty, independence and territorial integrity of all states and their inherent right to choose the means to ensure their own security, the inviolability of borders and peoples' right of self-determination as enshrined in the Helsinki Final Act and other OSCE documents"[1].
Even if we accept the premise that such assurance was given (which Gorbachev denied), then it was given to the USSR, which does not exist anymore. Former parts of that USSR themselves applied for NATO membership. Should their status be bound forever to a non-existing state?
Furthermore, this approach is based on disgusting colonial attitude that Russians are a some kind of master race that has the right to decide over everyone else, while ethnically they made up barely half of the population of the USSR. What about the other half? Do they not have the right to determine their future? Are they forever slaves of the ghost of the USSR?
[1] https://www.nato.int/cps/en/natohq/official_texts_25468.htm
No, Russian diplomats were not naive. They knew full well that whatever is not on paper does not exist.
It's surreal that 30 years later, we act like poor Russian diplomats didn't know that some random utterances made during long meetings won't be set in stone as an official policy forever.
Those people making such promises were not authorized to make binding promises anyway (something which Russian diplomats were aware of). There's a reason why agreement drafts undergo extensive analysis, vetting and approval process.
Their conclusion is not really deferent to either side's argument. Russia had every reason to believe in what was repeatedly said and implied, while the US had a justification in going against previous promises as the geopolitical scene shifted quite dramatically from when those promises were made.
Beyond this I'd emphasize in that geopolitical relations it's not like there's any law that forces countries need to abide their promises, whether spoken or written. If somehow there were a secret agreement in which the US overtly and explicitly agreed to not expand eastward in conditions identical to what happened, so what? Call on the UN to pass a meaningless resolution which the US would just veto anyhow?
And so in international relations, the perceived trust of a nation is ultimately far more relevant than the formality of an agreement.