Ironically enough, the Russian "mood" you describe could describe the US mood about our wars since 9/11. I think it didn't apply to Vietnam because we had a draft back then, but maybe I'm wrong.

We were all amped up to kick some ass - any ass - after 9/11. So we invaded Afghanistan (who didn't attack the US) and then Iraq (who didn't attack the US).

The first months, even years. the US people paid attention. Then it just became "the mid-east wars" and the news barely covered it unless something horrific happened (especially true for Afghanistan).

The US got so blasé about the wars that we had little "war-lettes" in between. Destroying Libya and turning it into a failed state with open slave markets. Nearly destroying Syria, invading the country and (to this day) occupying 1/3 of the country and stealing their oil. Etc. Etc.

We were in Afghanistan so long that generations of US soldiers were fighting there. It only became an issue when we finally left.

Maybe the US reacts so viscerally to Russia because we see so many similarities between our countries. We've been raised since birth to see Russia as an enemy. The cognitive dissonance between what we're told and what we see makes us angry and aggressive.