If Russia can't conquer Ukraine, what threat does it pose to western Europe and the US?
I went into more detail in the Shoutbox, but basically Ukraine has in three years set back Putin's plans for rebuilding Stalin's and the Czars' empire at least 10 or 20 years. Putin may not live that long, even if not defenestrated. Moldova and the Baltic countries were probably his next targets, but after those Poland was probably next on his target list.
Those clamoring for Ukraine to pay back what it has received are ignoring the service to Europe and the US that Ukraine has done by gutting the Russian military.