Although technically donations to political campaigns made by foreigners are illegal, ever since 2010's Citizens United decision greatly reduced limits on political contributions, companies based outside the US have been able to effectively circumvent such laws (I talk about just how murky US laws governing corporations have become here). In the last full election cycle, the first since the landmark ruling, foreign controlled subsidiaries contributed over $12 million to Super PACs on both sides, and that's just what was able to be traced. Due to Citizens United and other subsequent rulings, political action committees (PACs) that do not coordinate with campaigns and their donors are afforded great latitude when it comes to contributions, with no limits to how much can be given to such PACs, and little in the way of disclosure laws on the part of these committees. Major corporations didn't miss a beat, creating PACs through their American subsidiaries, and then drawing contributions from employees. This allowed them to influence U.S elections while at the same time shielding themselves from any chance of prosecution, But what if we could curtail foreign influence in the American electoral process while at the same time slowing or even stopping the exodus of American businesses and their tax revenues abroad?
Currently the American subsidiaries of foreign companies may make political contributions so long as the subsidiary in question is able to prove that it has funds drawn from domestic operations that equal or exceed the donated amount, as per this FEC advisory opinion (AO 1992-16):
FEC, AO 1992-16: The [U.S.] subsidiary must be able to demonstrate through a reasonable accounting method that it has sufficient funds in its account, other than funds given or loaned by its foreign national parent, from which the contribution is made.
As such when we examine recently "inverted" corporations, we see that the value of their American operations generally represent a disproportionate percentage of their total global revenue. For example Burger King, who recently announced a merger with Canadian coffee chain Tim Hortons in order to relocate to Canada, earned less than half (48%) of revenue in 2013 from territories outside of the United States. Burger King conducts the majority of its business in the United States through its Miami based subsidiary, and yet since its newly founded "parent company" will be based in Canada, it will only have to pay 26% income tax on revenue earned in Canada, and a rate consistent with the tax code in the country where any income that is repatriated was generated. While robbing the federal government of tax revenues, due to a very profitable US operation Burger King, should it be so inclined could spend millions on donations to PACs supporting candidates it likes.
While Burger King remains at its core essentially an American fast food company, it's unlikely it would feel the need to drastically influence policy, aside from more favourable tax laws (nothing seems to satisfy them nowadays) and looser labour regulations. But such loopholes present an opportunity to companies whose fortunes are largely tied to government spending and/or policy. The defence, (which currently has strict export regulations in place) education, health, food, pharmaceuticals industries have in the past tried to influence policies that would adversely affect them (See Pfizer's own proposed inversion via merger, or the HMOs' opposition to the ACA) and if they were to merge with foreign companies, what checks would be in place to limit their influence in American politics? By preventing subsidiaries wholesale from making political contributions, it effectively ices these "tax emigres" out of the legislative process, and helping determine where tax dollars they did not proportionally contribute go. American corporations and the people who benefit from them the most may not have the same interests as the vast majority of Americans, but they still live and work in the country, and as such do have a stake in a healthy and robust consumer base and economy.
Preventing the American subsidiaries of foreign companies from making political contributions will not definitively solve the problem of money in politics, nor will it stop the most determined of companies from relocating abroad. But it will make the decision a tougher one, unlike the no-brainer that it is. Admittedly, with Republicans currently likening these companies to "economic refugees" (but judging from their response to the influx of children from Central America, they really couldn't care less about actual human refugees), the chances of anything that makes life harder for the Burger Kings and Pfizers of American commerce being passed by this Congress is infinitesimal at best. Perhaps a more comprehensive solution including both cutting the corporate tax rate and closing these ridiculous tax loopholes would do better in coaxing businesses to return home. Maybe recognizing the sheer size of a corporation allows it to exercise its freedoms as a person much more effectively than a single American, and putting limits on that freedom would better check undue commercial influence in the legislative process. But in the meantime, piecemeal legislation such as this will have to do.