If you are subjected to propaganda, chances are high it is from your own government or companies operating on the domestic market.

The net certainly increased possibilities for foreign actors to reach domestic audiences, but claims of such cases are vastly exaggerated in my opinion.

That said, troll, shills, agitators and propagandists might have a good understanding of peoples fears and desires and will use that against you. More effective the more you know about the target. This is why surveillance is dangerous.