In all fairness, most European countries do have a single ministry/cabinet post responsible for all domestic security functions, but it is usually called Ministry of Interior or similar. US DoI seems to have different responsibilities (I meant to verify what exactly are these - something like national parks etc - but their web site is extremely unresponsive).

I agree with Bitt about significance of word choice ('Homeland', not 'Domestic'; 'sovereign right' etc). Speech and law writers are very careful bunch.