For once, Hitchens has the substance of it right: The security of someone who is living and working in the USA should be the responsibility of the US government.

It does not make much sense for this to be the responsibility of the Dutch government. Not on legal grounds, as this would infringe US sovereignty. And not on practical grounds, as it is highly desirable that her security detail is efficiently communicating with the local police and security forces. That she has Dutch nationality is neither here no there. The organization of security and police forces is territorial, not personal, for good legal and practical reasons.

After all the relevant institution is called "Department of Homeland Security" and not "Department of US Citizen Security."