Certainly both are happening, to one degree or another. Hostile influence campaigns are having some effect but I would give homegrown the most credit. Given the general bumbling of the Putin/Orban governments of the world I doubt they are overly competent in this one area. Most of the physical sabotage operations that have been uncovered in Europe weren't very sophisticated; even if they are still dangerous.

Americans are incredibly pissed about all sorts of things, both valid and absurd, and have a long track record of picking bad options as a fix.