From what I've read, if the U.S. hadn't meddled in Ukrainian politics, quite possibly playing a military role in the Euromaidan Coup, Russia would have left Ukraine's borders alone.
A good article on this:
U.S Sponsored Neo-Nazi Ukraine 2014 EuroMaidan. The Hiring of Snipers | Global Research
Afterwards, Russia accepted Crimea's referendum request to leave Ukraine:
Return to Russia: Crimeans tell the real story of the 2014 referendum and their lives since | Mint Press News
After 2014, civil war broke out in Ukraine between western Ukraine and the Donbass region of Eastern Ukraine. Russia tried hard to resolve this war politically, but to no avail. I think that former Swiss Intelligence officer Jacques Baud wrote a good article on this time period, as well as the leadup to Russia finally deciding that the only way to properly resolve this conflict was to intervene militarily. His article is here:
Former NATO Military Analyst Blows the Whistle on West’s Ukraine Invasion Narrative | Scheerpost