sorry but we're talking about 2 different things here. (1) a memo that says "we will pull our nukes from there and not invade or take it over" -- something akin to UN ideas of sovereignty and not using force on your neighbors -- and (2) an active commitment to the defense of ukraine. you're in NATO and if invaded we will all fight with you. a formal alliance.
(1) is not what the diplomacy/IR community understands as a security guarantee. USSR was not allying with ukraine, and not agreeing to have its back against invasion.
having, as you said, already had promises made promises broken by russia -- (1) and ceasefires since then -- ukraine wants something like (2) -- an actual security guarantee. peacekeepers, resident troops, or an alliance.
suggesting we USA gave ukraine a security guarantee in 1994 is wrong. wrong. wrong. we promised not to take the place over in the name of nonproliferation with the russians. which, let's be honest, was really russia promising not to invade.
last, since you seem confused, countries are allowed in the use of their sovereignty to join alliances or even host bases on their soil. that's their choice how to use their country. you seem to have that confused with russia exercising some sort of might-makes-right idea it controls both its country and its neighbors. which is at odds with the UN and rule based order. modern global politics.
you want to go back to wrestling over the planet, have at it, but don't pretend we promised things we didn't. that basically sounds like lame pro-russia excuse making. if we'd actually agreed to defend ukraine we'd have been there since 1994. if we'd actually brought them in NATO either this fight happens decades ago -- because they don't want NATO up to the border -- or it never happens -- because they know ukraine is in an alliance.
georgia and ukraine have gotten this precisely because they are nextdoor to russia and owed no alliances or security gurantees. and in the situation of georgia stupid people let russians serve as peacekeepers for a russian war.