How would the Iranian government (which seems to have replaced the Chinese as the traditional bad guy in these kind of plots) impersonate the root?
The only credible opponent in this game is the US government, which through coercion, legal or otherwise, openly or not (National Security letters, anyone?), could influence any of its subjects. But as I understand it the KSK can only be got at by corrupting three individuals, with most of them living outside the US of A -- see http://www.root-dnssec.org/tcr/selection-2010/ for your list of targets.
If the NSA wants to spy on your google.com traffic it is altogether more likely that they would attack com's key via rubber hose techniques, which is probably not as well-protected.