You are still ignoring the fact the assurances were made the US and Russia to Ukraine so the actions of the US should in no way invalidate the assurances both countries made to honor the borders of Ukraine. As to why Russia can’t act to protect their national interest that answer to that is by your logic any time a country can come with an argument that their national interest are threatened they can just take a bite out of their neighbors territory.
You have to admit how shallow the argument that that they are just protecting their base is and it sad that we keep hearing it. The base was never threatened so an invasion was not required to protect it. As to the safety of the Russian citizens they do have a valid interest they and if they had sent in observers to protect their citizens that argument might hold up but that isn’t what happened. The Russians have seized complete control and are in the process of illegally seizing a portion of their neighbor’s territory. In none of the examples you stated did the US end up with expanded borders. Using Kant’s categorical imperative would you be willing to accept the argument that believing some of your citizens that you believe might be threatened is justification to invade and seize territory from your neighbors?
As for the mysterious Olga who may or may not have evidence that protesters killed their own people I say it is irrelevant. I neither support not oppose the goals of the protesters but I do support the rights of Ukraine to their national borders and I strongly Russia’s use of this crisis as an excuse to steal territory from their smaller neighbors. The Russian people seem to be wonderful people with a deep and rich culture but their governments is run by thugs and thieves.