Stop Foreign Influence Act This bill amends the federal criminal code to impose a 10-year post-employment lobbying ban on a former President, Vice President, Member of Congress, or specified intelligence appointee who knowingly represents, or aids or advises, a country of particular concern. The term "country of particular concern" means: (1) a country designated by the Department of State to be of particular concern for religious freedom violations, and (2) any entity owned or controlled by such country. Additionally, the bill amends the Lobbying Disclosure Act of 1995 to revise the definition of "lobbyist." Currently, a lobbyist is an individual who: (1) is employed or retained by a client for compensation, (2) makes more than one lobbying contact, and (3) spends at least 20% of the time working for that client on lobbying activities. This bill broadens the definition to include, as a lobbyist, an individual who spends less than 20% of the time working for that client on lobbying activities, if the client is a country of particular concern and if the individual is a former President, Vice President, Member of Congress, or specified intelligence appointee.