Hi Nolm, I think it is quite a stretch to say US/Nato/EU/UK/Ukraine started this war. One could even argue that the West (from your options that being the US/Nato/UK/EU) actually abandoned Ukraine after Russia annexed Crimea and began an insurgency in east Ukraine in 2014 despite both the US and UK expected to support Ukraine as part of their Budapest Memorandum obligations.
One could argue that this muted response of the US/UK (and the West in general) to assure Ukrainian sovereignty in 2014 as pat of their Budapest Memorandum obligations gave Putin confidence that any response to a full invasion would be as muted.
The Cuba referrence you make has a couple of major differences to the present Russia Ukrane war. Firstly, the major difference is that no nuclear weapons were going to be stationed in Ukraine (the US was actually responsible for removing nuclear weapons from Ukraine, most definitely an act in Russia's benefit). Secondly, and although he US did attempt a botched invasion of Cuba (Bay of Pigs April 1961), this was before the Cuban missile crisis (October 1962) and thus the stationing of nuclear missiles in Cuba did not prompt the US to invade, as Russia has invaded Ukraine due to, according to you, Russian fears of a US/Nato/EU/UK presence in Ukraine.
