Answer:
Title of speech.
Step-by-step explanation:
The process of citing or providing a citation list of any text is made in such a way that the necessary details are given for the readers to make easy reference to it. Moreover, it also provides a way of legitimizing the given source of the text or (speech in this case).
In the given citation from President Obama's speech, the missing part is the first step of the citation format. This missing part is where the title of the speech is to be listed for a proper and correct citation. So, when the title of the speech is given, followed by the other details of the speech's source, dated and provided with the website source, then the citation is complete.
Thus, the missing section of the citation will be filled by the title of the President's speech.