One aspect of that which is a bit apples to oranges, is that the US is both incredibly easy for foreigners to enter and travel throughout, as well as being dive

One aspect of that which is a bit apples to oranges, is that the US is both incredibly easy for foreigners to enter and travel throughout, as well as being diverse enough that such travel wouldn't raise any eyebrows. At any given moment there are a million foreign people freely traveling around the US- some on vacation, some visiting family, some for school, some for work, some for medical treatment, etc. It's relatively trivial for a nefarious organization to find a person who speaks English and can legally enter the US. For Russia (among other places) none of this is true. Visas to enter the country are harder to acquire, movement within the country on such a visa is still constrained, a smaller number of foreigners means easier for intelligence to monitor, and far fewer people have the language skills or physical characteristics to blend into the local populace.