The main upshot of many features of the US political system that I don’t like is to enhance the influence of interest groups and decrease the influence of ideologues and technocrats. This is basically by design and reflects 18th century state of the art thinking about the dangers of liberal governance being trampled by demagogues. Insofar as the balance we’re currently striking is inappropriate to the conditions of the 21st century United States that’s bad for the right and the left.The part I put in bold, I think, is exactly correct. You really can't do better at explaining what makes the USA different. (For a bit more Yglesias on the subject, by the way, see here).
I think I'd disagree with him to some extent about the origins of some of the differences. For example, I've always understood (and I'm by no means an expert) that the relative weakness of the American bureaucracy is an artifact of the historical accident that the US began as a democracy without a bureaucracy, while in Germany and Britain, for example, bureaucracy preceded democracy. But while there are interesting and important arguments to have about the history of these things, what's far more important is whether in fact the American system -- interest groups more important, ideologues and technocrats less important -- is a good thing or not. Regular readers will know that I entirely disagree with Yglesias about this.
I want to keep this relatively short, but there are at least three grounds for objecting to his "ideologues and technocrats" version of democracy. The first is on political theory grounds: there's very little opportunity for meaningful participation in an extreme technocrats and ideologues system. Basically, voting is still meaningful, but that's about it. To really get involved, one needs to either develop ideological skills, which are generally narrowly held, or one needs to make a career in government. The American system, on the other hand, with traditionally non-ideological parties and fragmented and decentralized interest groups, parties, and governments, is inherently far more permeable, and thus encourages meaningful participation. Second is Madison's famous concern about majority rule. For Madison, majority rule democracies were inherently unstable, because high-stakes elections encourage the losers to defect (through, for example, civil war or coup).
And third, one can argue that technocratic systems aren't even more competent than the American system. Why would that be? For reasons similar, perhaps, to the reasons that command economies don't work very well. Bureaucrats, no matter how well trained, may find themselves both cut off from the people and with incentives that have nothing to do with good public policy (such as, for example, larger budgets for their agencies). Politicians with local, decentralized, particularized electoral incentives are (at least in theory) good at breaking through those incentives. Systems in which most pols are just time-servers and the only pols who really matter are in government, and attuned mainly to national incentives, are apt to be much less able to seeing when bureaucrats have gone wrong.
So go the arguments, in very abbreviated form. Just a couple other notes...I don't believe there's anything about this debate that does, or should, break down along right/left lines. Also, while I strongly believe my side of this is the correct one (thus the title of this post!), what I think is also important is to understand the choices, and see that it is a choice, and again I think Yglesias does a terrific job of that. And while I do think that the general outline of the American system is sound, that doesn't mean that every single veto point and every single check and balance is set exactly correctly (so in practice I think Senate reform is needed).