Technically England invading Scotland would be a better analogy, though even that is unfair to Ukraine as they were more important to the USSR than Scotland is to the UK.Lol dude. It was meant to be a super power. They're trying to invade what can only be summarised as Wales.
Ukraine were the second biggest nation of the USSR population wise (one Ukrainian for every three Russians) and had almost parity with Russia when it came to notable figures, technological achievements, etc. Plus notably superior ship building, tank development, nuclear missile development, etc. It was hardly some backwater and while the post Soviet years haven't been kind they haven't exactly bee worse than Russia faced, they have still been developing/selling weapons and were fairly well prepared to fend off an invasion despite what Putin and some idiots in the media thought. Hell one good example of Ukraine's importance is that Russia have only just built a dock capable of housing their Ukrainian built aircraft carrier (which is falling apart after 20 years of no real maintenance) and they are currently scrambling to reverse engineer their Ukrainian ICBMs as for obvious reasons the maintenance contracts have been voided xD.
An interesting note that not many know but some may find interesting is that a Ukrainian (Leonid Brezhnev) was the second longest serving leader of the USSR, behind some Georgian bloke name Joe. And not just that but he ruled the USSR for almost as long as every Russian leader combined. The idea that Russia was the only important/contributing country in the USSR is simply post Soviet Russian propoganda.