If I were a political theorist, or if I were capable to do an in-depth qualitative case study, I would pick something related to the origins and evolution of so-called "legal traditions"--and freedom of speech would rank very high on which traditions to study.
The Exceptional First Amendment
Harvard University - John F. Kennedy School of Government
KSG Working Paper No. RWP05-021
As is increasingly apparent, the United States is a free speech and free press outlier. With respect to a large range of issues - defamation, hate speech, publication of information about ongoing legal proceedings, incitement to violence or illegal conduct, and many others - the United States stands alone, not only as compared to totalitarian states, but also in comparison with other open liberal constitutional democracies.
The reasons for this divergence are common, but among the explanations are the complexities of the trans-national migration of legal and constitutional ideas, differential commitments to libertarian visions as a matter of basic political theory, differences in the constitutional text, differences in political and legal history, differences in the role of various interest groups, and differences in views about constitutionalism and the role of the courts. This paper attempts to explore in an explanatory but non-evaluative way the causes of American free speech exceptionalism.