I don't think there's a need to defend against it. You can acknowledge that the US has done some fucked up shit. The invasion of Iraq was, as far as I understand it, based on outright lies from the Bush administration about evidence of nuclear weapons in Iraq. Just say, yeah, the invasion of Iraq was fucked up. This invasion of Ukraine is also fucked up. We should condemn both.
There are probably nuanced arguments to be made about which is worse. You could maybe argue that attacking a NATO-aligned country is more dangerous for world peace than attacking Iraq was (at least from a western perspective). You could point to the fact that there's no reason to believe Putin will stop after Ukraine if that attack goes well; his "excuse" for invading Ukraine applies to most former Soviet countries. But you don't have to defend US invasions, you can accept that at least some US invasions are bad even if you generally prefer US hegemony to Russian or Chinese hegemony (which I also do, FWIW).
That is pretty good summary of the sentiment of most people (US and Europe) and I cannot say my sentiments are very far off from this (we speak about high level outlook, not the details of war crimes perpetrated in Iraq, and elsewhere under US aggressive wars).
However, objectively, one cannot with the same breath claim and act as if there are no other world views and values and interests (China, Russia, Middle East, etc), which is dismissed apriori or even vilified.
I wonder whether my own leanings are not just a results of the easy life (materially) which is an end result of wealth extraction by US and EU from the poorer countries (assured by policies of economic or military). When I talk to friends from the Middle East or Africa who live or lived on the other side which is used to extract wealth for the west, have very different opinion/view. One might be surprised to learn what ME average person think about a westerner (as an abstraction).
In summary, living under hegemony in prosperity (and a future assurance of it) it is easy position to defend and take security in it (and its values). However, being or living on the other side of this equation one is confronted with different view.
Kenya's representative to the UN made a very strong statement against Russia invading Ukraine.
Non-Western non-superpowers are no more excited about being kicked around by Russia and China than Western ones. Western hegemony hasn't been all good for them, but it beats the amoral free-for-all that self-loathing Westerners wish for.
It is important to remember that there were two Iraq wars, that the first was aiming at the wrong party (Iraq had no hand in 9/11), and that the second was based on either faulty or fabricated intelligence.
Thanks, yes, this seems like a good stance. I am pro-US because I believe in the values communicated - these values apply globally, if you want to believe in it (and I want), even if you're not US citizen. I don't see any values for outsiders in Russia's system.
There are probably nuanced arguments to be made about which is worse. You could maybe argue that attacking a NATO-aligned country is more dangerous for world peace than attacking Iraq was (at least from a western perspective). You could point to the fact that there's no reason to believe Putin will stop after Ukraine if that attack goes well; his "excuse" for invading Ukraine applies to most former Soviet countries. But you don't have to defend US invasions, you can accept that at least some US invasions are bad even if you generally prefer US hegemony to Russian or Chinese hegemony (which I also do, FWIW).