Calling Siberia or Kamchatka Russia's backyard might be accurate. But just like Canada isn't America's backyard neither is Ukraine - or any other former USSR vassal state - Russia's backyard.
Neighbors is an entirely different term.
As for Europe-Russian disputes, there is such a thing as NATO, which was good enough to be relied on after 9/11, I take it that it is still in force? If not can you point me to the news that I apparently missed?
>An area nearby to a country or other jurisidiction's legal boundaries, particularly an area in which the country feels it has an interest. https://www.yourdictionary.com/backyard
Which seems spot on, I swear I didn't just write that myself. The WSJ even went so far as to call Equatorial Guinea (in West Africa) part of America's backyard: https://archive.fo/8UjYC
"In my own backyard" would connote what you are saying, but there's an extra word "own" there.
That's like saying that United States and North America are "neighbors". Is that "true"? Or is it a category error?
Wow, this must be a new low in these threads.
No, Eastern Europe is Europe's 'backyard', and in fact it isn't a backyard. Romania, Poland, the Baltics, Hungary, Czechia, and so on are all solidly part of Europe.