Basically, it boils down to: the British definition of "liberal" is the correct definition, the American definition isn't so much incorrect as nonexistent, and there is no need to study the history of the word, "liberal," or its usage in American politics if you actually want to understand what it means in America, because Britain is intrinsically more correct in all things linguistic.
Oy.
Look, you know I hate to be snarky. It's just... not in my nature to snark. Really, though, there is history for the term, "liberal," in American politics that deviates from its usage in Britain. In Britain, Broich is correct in his definition. In the US, contrary to Broich's central thesis, "liberal" means left, and "conservative" means right. That's why, in the American National Election Studies and similar surveys, we ask people to place themselves on a left-right spectrum from liberal to conservative, and do the same with scales for Congress, and so forth. The fact that Britain uses the terms differently is irrelevant. There are plenty of linguistic differences between British English and American English. This is one of them.
However, people who don't study American politics, but study European politics, or British politics, get tripped up in the wording, and find themselves unable to understand the wording difference in American politics. Then, problems ensue. I have actually written about this before, in my excoriation of the term, "neoliberalism." Everything in that post applies to Broich's attempt to lecture us lowly non-British historians who dare to try to talk about American politics in our own terminology rather than British terminology.
I believe that if we had Ralph Waldo Emerson back, he would find some erudite way to tell such scholars to go stick it where the sun don't shine. That would be Britain. (Technically, though, that's Cleveland too, so that doesn't really help me much in this argument.) One of the essays that held special importance for me was The American Scholar, in which Emerson implored students and his fellow American literati to stop looking to Britain and the continent as some sort of intellectual holy-land to which they must all bow, like Mecca, and instead develop their own thoughts and traditions, independently.
To some modern day Americans in the academy, I'm not sure Emerson's entreaties have carried much weight, but really, people, hasn't our day of dependence, our long apprenticeship to the learning of other lands drawn to a close? Watch me refrain from any use of the term, "sluggard intellect." I liked Emerson. He was so much cooler than Thoreau.
Anyway, my point is that the 20th Century American political tradition really was different from the British tradition, and its language branched off to compensate. That happens. There is no logical reason for the difference between the -or and -our thing, but in a constrained wording system, inventing new words as coalitions shift would be silly, so the words that describe ideological coalitions shift as politics shift.
Remember, an ideology is not a logical belief system, in practice. British historians rarely read Converse's 1964 article, explaining that an ideology is a bundle of policy positions that are tied together with a set of constraints, only some of which are logical. The others are psychological, and sociological. Moreover, as the social dynamics change over time in ways described by Noel, the ideological coalitions shift and the bundles of policies within any given label shift. Hence, the labels have constantly, slowly-shifting meanings. So, we can either watch in annoyance as the words evolve, which I don't like, linguistic prescriptivist that I am, or we can invent a new word every year or so. That seems less practical to me, even though I am a prescriptivist. The result is that I recognize that the word, "liberal," doesn't mean the same thing today in the US that it did 20 years ago, nor the same thing that it means in Britain.
For some reason, though, people who are a) scholars, but b) scholars of something political but not American politics can never grasp this. Those of us who are scholars of American politics have no difficulty understanding that "liberal" just has a different meaning in modern America. And we get really sick of people telling us that we are the ones doing it wrong.
If we designed our surveys differently-- if we designed the NES survey around Broich's concept of the word, "liberal," American survey respondents would have no clue what we are asking, and the survey would fail.
I'd like my surveys to succeed, thank you very much, and that means speaking in the language of American politics. And if we asked about "neoliberalism," which Broich addresses, nobody in America would have any clue what the question is asking because nobody in campaigns or the news uses the damned word. I don't care how useful British scholars think it is for Britain, because that has nothing to do with the price of tea that has been thrown into the Boston harbor. And no, I'm not using a "u" in the word, "harbor."
Is this how you do it, Ralphie?
It is also worth discussing, though, that ideological labels seem to be in the process of changing again. How often do you hear candidates describe themselves as "liberal?" That stopped happening with any frequency a few decades ago. Mainly, that's because the GOP-- Reagan especially-- turned it into an epithet. It didn't used to be! And when it wasn't, candidates had no problem self-applying it. However, once it started to get more negative in its associations, "left"-wing candidates began shifting to the term, "progressive," which is how they are much more likely to describe themselves now. Over time, the word, "progressive," could replace, "liberal," in American politics, and people like Broich may be happier.
Of course, American history scholars should then get their hackles up because there actually was a "progressive" movement around the turn of the 20th century, and the modern-day "progressives" really don't have a lot in common with them! So, some jackass could come along and write a Broich-style piece about how everyone needs to know about the difference between "left" and "progressive," and blah, blah, blah, history repeats itself, except that I can't do the Emerson thing because the progressive movement was an American thing, so I'd be snarking on an American history professor.
Really, though, why are we doing this? If we want to go this far, do you remember where the terms, "left" and "right" originated? It was about where you sat in the chamber of parliament in France, and power arrangements there. Once you get away from that, should we still use those terms? If I follow Broich's line of reasoning, I'm going to call bullshit on the terms, "left" and "right." Or... just go with me for a moment.. we recognize that over time and across national boundaries, the labels we use for ideological groupings will change meanings because the politics of any given country will change over time, and unless we invent a new word every couple of years for the subtle changes that have taken place within an ideological coalition, we just have to accept this.
Think about who is writing this. I am the grammar-nazi who tells you that you must treat "data" and "media" as the plural terms that they are because there is meaningful content to the singular/plural distinction. I am as prescriptivist as you can get. If I am the one telling you that you must accept these changes to language because the words must evolve in response to political changes, what does that tell you?
It tells you that the people resisting it aren't doing it out of prescriptivism. They are doing it because they don't study modern American politics, and are trying to be smugly superior about it.
The American National Election Studies survey has not been asking its questions incorrectly since its inception half a century ago. Those of us who study ideology in American politics professionally actually select our words carefully and correctly. We're just a different country from Britain, and I not-so-humbly suggest that if you want to study what the word, "liberal," means in American politics, the key is to study the history of its usage in American politics rather than glossing over most of it in favor of Britain, because ultimately, that was what Broich did. He wrote about what "liberal" means in Britain, and America's left, but he didn't address the history of the word, "liberal," in America until he had an excuse to use that loathsome word, "neoliberal," by attaching it to Clinton, by which point the actual American left had stopped calling themselves liberals because Reagan turned it into an epithet against the left!
Oh, Ralphie. Where are you when we need you?
Oh, right. Dead. Damn. I guess you couldn't transcend that!