The US does not have an official language because it chose a different path. As Ukraine is mostly a monoethnic state, it seems logical for people to be unified by one official language. Besides, if Russian is the official language of the RF with over 140 million speakers, why this sudden need to protect it? Protect from what?
As you mentioned above, most people in Ukraine understand and/or speak Russian, there are still many schools where Russian is taught. However, I challenge you to find a single school in Russia where Ukrainian is taught. Belarussians and Ukrainians understand each other, as well as Russians, pretty good, and yet Russians do not understand Ukrainian and Belarussian languages but somehow laugh at how ridiculous they are.
My grandparents spoke Ukrainian, I grew up speaking Russian as my first language. The Donbas region gradually became russified during the 20th century, with more and more people forgetting that once the majority of population spoke Ukrainian there. Moreover, people in Kuban also spoke a form of Ukrainian once. But none of your Russian friends will tell you that because it doesn’t fit their version of events.
I’m not saying that all people of Russia are bad but if there is a language that needs protection, it is most certainly not Russian.