One thing to remember about multinational oil companies is that they are multinational. Every country has laws effecting these companies and the US has more than most. Environmental, labor, excise (mining) and property laws, shipping and transportation laws are a contradictory patchwork of laws designed to subordinate the interests of the owners of the multinational oil companies' interests to those of the states'. I would argue that the US congress is no more qualified to manage an oil company than they are to manage education. Further, if political groups in the US or elsewhere are willing to be bribed then management of companies should do so when it benefits the interests of their shareholders.
Neither companies or individuals have a moral obligation to support a state who's laws are created to, in large part, advance the political careers of a few well placed individuals and promote the acquisition of wealth by the state or its political parties.