HMARS could make a difference if two things were true: (a) the USA supplied enough launchers and rockets to make a real - as opposed to PR - difference, and (b) the USA supplied long-range rockets capable of hitting Russian bases inside of Russia itself.

As neither of these things are true, HIMARS-related stories are little more than window-dressing, continuing to play the role of distracting western voters from the fact that the west is in reality doing almost nothing of real value to stop Putin's annexation of huge swathes of Ukraine and then committing endless atrocities against unarmed civilians that news media no longer report because it would make us all look as bad and as ineffectual as we really are - which would be terrible for ad revenues. So instead we get "look how great HIMARS are" storied that are totally non-indicative of the real-world battlefield situation. Putin knows he can simply outlast us because we're feeble-minded, lazy, and self-indulgent with very short attention spans.