As far back as the 1830s, de Tocqueville made a fascinating study of why a stable democracy had arisen in the wake of the American revolution of the 1770s while, in contrast, the French revolution of just a few years later had led to mass slaughter and the guillotine. In significant part, he found that the difference lay in the massing of power that in France had gone unchecked, leading the people to fall under the sway of their immediate, unchecked passions and causing disastrous results.
In politics, there are reasons to check unlimited power and the U.S. system of law and politics is fundamentally premised on this (that is why there are, among other things, three co-equal branches of government, a federal/state division of power, a bicameral legislature, and, ultimately, a constitution whose main function is to prevent the rise of an overweening central authority).
One can of course question this and advocate for a stronger central authority and for the abrogation of the various checks and balances (or even pure traditions, such as the filibuster) but it is a bit tendentious to say that a system has suddenly become "ungovernable" simply because you wish it did not stand in the way of your immediate agenda. It has, after all, been but a very few years since many of these same sources were touting the filibuster as the last, great bastion of liberty when it was being used by a then-minority party to block judicial appointments seen as unfavorable to their cause. One's arguments are always stronger if they are principled and not tied to the exigencies of the moment, as those advanced here appear to be.