what makes you think that Russia has infinite resources? Reading reports from various parties, it seems obvious that Russia is already suffering considerable difficulties in supplying their troops.
As to the goals, whilst I am not a politician it seems likely that Europe and the US view this as necessary in order to stop Russia from continuing to aggressively expand their borders, as this is not the first country they've done this to (e.g. Georgia).
Therefore As long as the Ukranian people want to continue to fight, it would seem to make sense for the western powers to support them in doing so.
Also, I don't think you're comparing like with like. In Iraq, the US was essentially an occupying force, where there were considerable factions of the population who did not want them there.
In Ukraine, Russia is the occupying force and there are obviously a large number of people in Ukraine who do not want them there.
As to what this particular attack does, there are a couple of obvious consequences.
1) Propaganda victory, it shows a previously assumed safe target is not safe, increasing pressure inside russia from citizens who do not want to be targets
2) Logistics. This further disrupts the flow of munitions and supplies to russian forces in Crimea and Kherson region. Ukraine has spent a lot of effort on targeting supply lines as a means to weaken russian defences and lessen the effect of their attacks.