The Kuwait war was after an invasion by Iraq and at the invitation of the government there, and the US were restrained enough to halt at the Iraq border.
The Syrian war was not started by the US, and it has played a minor part there. In fact, it is Russia that has indiscriminately bombed Syrian cities and targeted civilians and hospitals there.
Afghanistan was in response to 9/11 and the refusal of the Taliban to end their protection of a terrorist organisation that had repeatedly attacked American targets internationally before their deliberate targeted murder of thousands of American civilians. This does not seem comparable to Ukraine.
The Iraq war stands out for me as the unjustified and imperialist war of modern times. It seems to me that the atmosphere post 9/11 was used as a pretence. But even Iraq does seem different: Hussein was a brutal dictator and, at least initially, Americans were welcomed as liberators. In Ukraine we are seeing widespread civilian resistance to the invasion. But Blair and Bush should answer for their war crimes.
By far the biggest difference here, I think, is that by being a European war and through the potential for further conflict and nuclear conflict, this war has far larger international ramifications and strategic risks attached to it. To see European cities bombed is to be reminded of what has happened in the past and that it can happen again. That is why it is receiving so much attention.