[lancium]

http://www.fec.gov/pages/brochures/foreign.shtml

The ban on political contributions and expenditures by foreign nationals was first enacted in 1966 as part of the amendments to the Foreign Agents Registration Act (FARA), an “internal security” statute. The goal of the FARA was to minimize foreign intervention in U.S. elections by establishing a series of limitations on foreign nationals. These included registration requirements for the agents of foreign principals and a general prohibition on political contributions by foreign nationals. In 1974, the prohibition was incorporated into the Federal Election Campaign Act (the FECA), [HTML] [PDF] giving the Federal Election Commission (FEC) jurisdiction over its enforcement and interpretation.

[justlurking]

I read through all that, and it appears that a foreign contribution to an 501(c4) advocacy group is allowed.

AUFC is indeed a 501(c)(4) group:

Americans United For Change is organized under section 501(c)(4) of the Internal Revenue Code.

Such a group is a "social welfare organization". But, lobbying is a permissible activity:

Seeking legislation germane to the organization's programs is a permissible means of attaining social welfare purposes. Thus, a section 501(c)(4) social welfare organization may further its exempt purposes through lobbying as its primary activity without jeopardizing its exempt status.

However, there are restrictions:

The promotion of social welfare does not include direct or indirect participation or intervention in political campaigns on behalf of or in opposition to any candidate for public office.

However, that doesn't prevent them from supporting or opposing a candidate, as long as it isn't their primary activity. And, they must be independent of the candidate's campaign.

More information here:

Political Campaign and Lobbying Activities of IRC 501(c)(4), (c)(5), and (c)(6) Organizations