backyards
A backyard is an area of land at the back of a house.
If you refer to a country's own backyard, you are referring to its own territory or to somewhere that is very close and where that country wants to influence events.
They seem to think that if it isn't happening in their own backyard, it isn't worth worrying about.
他们似乎认为,如果事情不是发生在他们本国的后院,就不值得担心。