A significant population of east Ukraine has family in Russia. This is like New York invading New Jersey. Ridiculous and terrible but they are aware that their family and friends live there.
There are hundreds of videos of Ukrainian civilians trying to climb aboard moving Russian convoys and blocking their paths and knocking out their mirrors and the Russians doing their best to ignore it.
Would it have been possible for Iraqis/Afghans/Syrians to do this to the US army?