I suppose if Rav Schachter says that, he must think that.
But the most natural reading is that he is talking about dina dmalchusa in general–otherwise, does he think there is one reason that applies only to taxes, and one reason that applies to everything else but does not apply to taxes? (because if there is a reason that applies to everything else, he’d need to distinguish why it also doesn’t apply to taxes or doesn’t also apply to eretz yisroel).
also: http://www.hebrewbooks.org/shas.aspx?mesechta=16&daf=28&format=pdf