The obvious response
When a Government site (any Government, not just the US) is hijacked in this manner, the obvious - and appropriate, and measured - response is to launch a major, deliberate denial of service attack on the site(s) in the link(s). Governments have the power (and the legal right - I won't talk about ethics nor morals, since no Government has ever had more than a nodding acquaintance with either of those) to defend themselves against attack, and this is certainly an attack.
Furthermore, if the Government in question wants to permanently discourage such attacks, competent IT security blokes (and/or blokesses) should be immediately put on the trail of the ultimate beneficiaries of the hijackings, and once located, their assets and persons seized. Let's put Gitmo to some "good" use for once!
But that will never happen, because, as is all too obvious, competent IT people avoid Government jobs like chavs avoid work.