I don’t know. Seems like the Orban government was funneling an awful lot of money to CPAC. You know, one of Putin’s closest allies. Not sure it’s genuinely home grown.
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.
The amount of "foreign" money in US politics is absolutely dwarfed by the amount of "local business" money. The US government is being dismantled by its corporations, many of which are home grown.