Why has the Russian invasion of Ukraine grabbed and held international attention? It is not, sad to say, the only example of armed conflict right now or in recent years. And Americans, in particular, are not known for being gripped by foreign affairs. So what makes Ukraine different from other conflicts? Here are a few (non-exclusive) potential explanations.
First, Ukraine is a European country being invaded by another (coded-as) European country. That, for better or for worse, makes a difference, though I don't have much more to add to it.
Second, it's a (relatively) evenly matched hot war conflict between two (relatively) modern and modernized military powers. Most of the major military confrontations involving modern militaries in recent years have been cases where one party is far more powerful in conventional terms than the other (e.g., either of the Gulf Wars). The traditional "war" part of the conflict was pretty much a walkover; any difficulties came later in reconstruction and/or insurgency. Here, neither side has the ability to decisively demolish the forces of the other in the short run even as we remain in a phase of traditional battlefield confrontation as opposed to guerilla resistance and insurgency/counterinsurgency.
Third, the war here involves a relatively stable, relatively liberal democracy on the defensive, being invaded in an existential threat to its existence. That is quite rare in my lifetime. Cases where, say, America has been attacked by illiberal forces tend to be sporadic and asymmetrical terrorist events; America certainly hasn't experienced nor has been at any substantial risk of an invasion in decades, or any other assault that poses a genuine existential risk of seeing the country dissolved. That's been true of most of our European allies as well; ditto countries like Japan or Australia. To see the liberal democratic camp on the defensive like that is, I think, quite shocking.
Other factors I might be missing?