Well, so here's the question: what counts as the interests of a foreign country? AIPAC's entire lobbying stance is that its positions are mutually beneficial to both the US and Israel, and this is the stance that every other national/ethnic affinity group in the US uses as well.

Put another way: it seems very risky to allow the federal government to determine the propriety of political speech just because it happens to concern two (or more countries) at once.

The difference is the nature of the lobbying and the volume. Follow the rules.

An egregious, non-controversial example of things going poorly is NYC Mayor Adams and Turkey. He basically accepted bribes and favors from the Turkish government and their proxies for specific actions.

A “doing it right” example that wouldn’t have been controversial until recently is Denmark. They mostly focus on direct diplomatic policy lobbying, and leverage consultants to promote mostly tourism. Their affiliations are known and registered. Now they hire K-Street lobbyists to influence policy objectives re: Greenland, etc.

The difference is that when the papers found out about Adams being a crook… that didn’t turn into accusations of racism and fomenting sectarian hatred. In the AIPAC example, there will be a both a legitimate visceral response from Americans and astroturf from lots of prominent people.