The federal rule also allows a party to serve a corporation in the United States “by delivering a copy of the summons and of the complaint to an officer, a managing or general agent, or any other agent authorized by appointment or by law to receive service of process.” (emphasis added). Although this has a relatively straightforward application in the case of a U.S.-based corporation, it is conceivable that [Y] might seek to avail itself of this means even as to [Y].