We outsiders are all spectators. Only the invaded can speak of the real "indignation" - I spent my early years in Iraq during Saddam's worst days - here's what life was like
If you are asking whether some Americans were pissed at their government for invading Iraq (whatever the pretext), yes they were. Protests against the Iraq War cites that in 2003, around the beginning of the Iraq war, anti-war protestors were a vocal minority. But by 2007, (according to a Gallup poll) most Americans believed the war was a "mistake". Nevertheless, the Iraq War didn't generate as much political agitation in the US as the Vietnam war, unlike in Europe which did see large anti-war demonstrations.
What about today in Russia vis the Russian invasion of Ukraine? Currently, the support for the invasion to fight "Ukranian Nazis", integrate Crimea with Russia and annex other Russian speaking border locales in Ukraine is quite huge - Russians think they’re engaged in a heroic struggle with the West.
Now, the question is will this support last? Or will it wane like it did in America with the Vietnam war, the Iraq war and the Afghanistan war?
It's hard to say because for the Americans all these wars were being fought in a far off foreign country, against foreigners that Americans couldn't culturally relate to, and the war itself didn't really endanger ordinary resident Americans. The Russians however have a more vested interest in Ukraine as they believe they are fighting their own people whom they know and once respected (Ukraine is considered as a "brother nation" by Russians). And they genuinely believe they have a claim to the land they are trying to seize and annexe. Moreover, the Russian politicians and military are convinced that these annexations are strategically vital to their national security. (Americans probably experienced something like this only during the Cuban Missile Crisis and during 9/11).
But of course, historically, any war that drags on tends to become unpopular. Especially if people are forced to fight these - drafts during the Vietnam war proved hugely unpopular and Russians are now being conscripted (and some are definitely trying to dodge it). The Russian leaders are aware that long-drawn out conflicts isn't politically good for them and as per a Russian propaganda news site, Russian politicians are already trying to prepare their citizens and are warning them that the war may go on for another few years - A confession from Putin suggests that the Ukraine conflict could last for years.
Note: Many western media do acknowledge that there is public support among Russians for the war. (See here, here, here, here, and here for more info). They also try to be dismissive about it by claiming that it is so because of strong government propaganda. That's misleading and dangerous because it tries to minimise the fact that people believe the propaganda and are convinced by it.
That said, new propaganda (like trying to convince people of a new political situation, like a war) is often difficult to sustain in the long-term in the face of reality. When the Americans failed to achieve the objectives of their war, and the returning soldiers revealed the ugly truth of war to the general public, popular leaders and government lost support of the people.
Both Ukrainian and Russian leaders will similarly soon face this, especially if the war continues to drag on for a long time.