Hasn't that traditionally been a large source of US influence? I don't mean paid political consultants, but government officials advising politicians in and out of government, outside of diplomatic channels? Certainly played a significant role in, say, Germany.
I think there's also the problem that such laws are extremely easy to misuse to shut down voices one doesn't agree with. I think there's a fair argument to be made that countries with strong institutions including sep of powers, can benefit from such rules.