Diversity is not a cause of action. It is a basis for jurisdiction to file a civil lawsuit in U.S. District court when the case does not involve either an issue federal law and the federal government is not a party to the case. The foreign government agencies & defendants would generally not be subject to the jurisdiction of any federal court, except that foreign person who have some connection/contacts with the U.S. might be subject to being sued in the U.S. As the plaintiff in what I assume was a lawsuit in federal district court (since you mention diversity) it is your burden to show both subject matter jurisdiction and personal jurisdiction. The foreign agencies and defendants being dismissed for want of jurisdiction wouldn't necessarily result in the dismissal of the entire case. Was the landlord foreign, too (i.e. was your entire complaint about something that occurred outside the U.S.)? If the answer is no, then why was the case against the landlord dismissed? Lack of diversity?
While an employer could find out about your federal lawsuit by searching PACER, which is the system used by federal district courts and appellate courts to keep track of case information and which is available to the public, most employers wouldn't bother to do that unless some kind of special background check were needed.