No, that's not an accurate characterisation. You're confusing the cause and the response. That the support to Ukraine has been predominantly US-led, in no small part because it had stockpiles that Europe does not, does not tell us anything about Russia's motivations for invading a sovereign neighbour. It's also possible for countries to support what they consider an ally without it being a 'proxy' war. For it to be a proxy war would require that NATO caused the war, but all the historical evidence shows that NATO countries like the US, France, the UK, Germany, and others spent months in advance of Russia's invasion trying to convince Putin not to invade. There's even a video of one of Macron's phone calls to Putin where he begs him to agree to a diplomatic summit that could find an alternative to war.

Chomsky's view, and I'm guessing yours too, is that NATO should never have expanded, that NATO's expansion was a move intended only to provoke Russia, that Russia had the right to not have NATO on its borders, and therefore that Russia's invasion of Ukraine is justified and understandable.

Yet none of those are accurate, as I've shown, but I'll address them again in brief below:

1) NATO was expanded only with initial great reluctance and the constant lobbying of Eastern European and Baltic nations in particular, who had good reason to want to be part of a defensive security alliance. However, and most importantly, Ukraine was nowhere near joining NATO and certainly was not moving closer to it in January/February 2022. There was, in fact, no activity being undertaken by Ukraine that could possibly be considered a clear and imminent threat to Russia in any form.

2) The expansion was conducted cautiously, with strict limits placed on what forces could be forward-deployed near Russia, adding Russia as a Partnership for Peace member, creating the NATO-Russia Founding Act and with it the permanent NATO-Russia Council, and creating additional official liaison offices to provide the Russians with visibility into and reassurance about NATO's operations and intentions.

3) Sovereign countries are free to join whatever security alliance they want to, it is a fundamental concept of sovereignty that countries should have their own foreign policies. Therefore Russia has no right to prevent its neighbours from joining either the EU or NATO. To grant Russia a veto over that would be to accept an undemocratic imperial hegemony of the type that existed decades ago. Of course, Russia is free to use its own foreign policy instruments in response, by isolating, sanctioning, demarching, etc a neighbour that does something it doesn't like, but that's as far as it can go.

4) Obviously, given all the above it's ludicrous to claim that Russia had any kind of justification in invading Ukraine, or that its decision to do so can be viewed as an understandable or reasonable one.

But sure, if you still want to argue that it was 'because of NATO', then you have to accept that Russia chose to invade Ukraine not because it was about to imminently join the alliance in the next few months (because it was years and years away under the absolute best case scenario) but to avoid the mere possibility of it joining NATO some point in the future. That's no less unacceptable and illegal, and it doesn't make it more understandable.

Would you accept the US invading Venezuela because it was concerned about that country's close alliance with Russia and substantial re-armament using Russian weapons?