Bad answer on my part: The USA already funds elections around the world so maybe it is fair if we allow the same (I am not happy with this solution but it is a fair point you made) but as long as everyone knows the origins of the money we should be OK.
Personally I don't want any foreign corporation or any American corporation which is owned by foreign citizens or controlled by foreign citizens or foreign countries influencing the elections by donating money to candidates for election in the United States. Period.
I don't want to have to compete with the Communist Chinese or the Saudi Arabians for influence in who gets elected and which laws are passed. Every nickle that a foreign country contributes to our election process is a nickle that dilutes my own power as a citizen of the United States.
I don't think there should be any limits on donations made by individual citizens of the United States, but clearly that right belongs to the individual citizens and not to some entity created by statute that can be controlled by foreign citizens or foreign countries.