Question for discussion: If those on the right are now defending the rights of foreigners to spend money in American elections, what to make, in retrospect, of the whole flap over the injection of Indonesian and Chinese money into the 1996 Clinton campaign?
The New York Times, for what it's worth, says "in his majority opinion in the case, Citizens United vs. the Federal Election Commission, Justice Anthony Kennedy specifically wrote that the opinion did not address the question of foreign companies." The Times also says the Foreign Agents Registration Act "already prohibits independent political commercials by foreign nationals or foreign companies."
Most foreign firms that operate in America have American-based subsidiaries or affiliates, anyway, so it becomes a bit of a tough line to draw. Would, say, Toyota Motor Sales USA have the right to air ads telling voters to oppose the congressmen who took the tax dollars of American Toyota workers and dealers and used them to bail out General Motors? It probably should have that right under the First Amendment, even though it is an arm of a Japanese company. But should, say, the government of Iran have the right to buy commercials on American television telling voters to oppose Congressmen who favor sanctions on Iran that make it illegal for an American TV company to even accept the funds to air those commericals? As a policy matter, it's debatable, but as a matter of law, if Congress said no, would the Supreme Court overturn the restriction on First Amendment grounds? Probably not: my own guess, having read the full Citizens United opinions and dissents, is that the current Supreme Court would uphold restrictions on foreign campaign ads if Congress made clear in the text of the legislation that it was written on national security grounds. Either way, it's a more complicated issue than President Obama described it as in the State of the Union address.