There's a difference between it happening, and it happening so often that it can be taken for granted. The CIA trying to plant microphones into stray cats hoping they'd wander within earshot of Soviet dignitaries happened too.
The truth is, it isn't known, the scale of these operations, and you can assume everything is full of spooks or not. But the more reasonable assumption, absent evidence to the contrary, is that it's likely not a conspiracy. Particularly when you're describing points of view which a lot of Americans actually do hold.
Although then I suppose you could suggest that the reason Americans believe certain things, or even the appearance of that belief, is the result of propaganda but, again - who knows?
