Citizens United said that US corporations can spend unlimited "independent expenditures for political campaigns".
However, foreign natural persons and foreign corporations are not allowed to spend any independent expenditures for US political campaigns. Even buying merchandise from a presidential candidate's campaign website would be illegal for a foreign natural person or a foreign corporation.
However, for a US corporation that is 100% owned by foreign natural persons, does Citizens United apply? What about 99%, 98%, 97%, .... ?