Fair enough, you're right that the external clitoris is more closely analogous to the glans penis than it is to the penis entire. However...
It's important to remember that such comparisons of FGM with MGM depend on the criteria.
For example, by the objective criteria of neurological damage the amputation of the male foreskin is worse than amputating the external part of the clitoris because the foreskin has more nerve endings which are permanently lost with the amputation.
On the other hand by the criteria of lost sensitivity the amputation of the external part of the clitoris comes as worse because the density of the nerve endings there is higher.
Further by the criteria of loss of sexual function in both cases some function is lost, and it gets more difficult to say which loss is worse in comparison without defining further criteria. By the subjective criteria of lost sexual pleasure comparisons becomes even more fuzzy because after all the most important human sexual organ is the brain and there's large variation in subjective experiences. And it's not a competition anyway.
There's also spectrums:
Not all MGM are the same and practises, severity and results do vary.
Also FGM entails a wide spectrum of practices varying from symbolic circumcisions without permanent injury to amputation of healthy tissue and even infibulation. Yet they're all female genital mutilation as per WHO.
For example, would you say that scraping or pinching female genital tissue without causing permanent injury is worse than the partial or total amputation of the male foreskin?
I believe not, as that would just not make any sense. Yet, when someone says 'FGM is much worse than MGM, and you cannot compare them' he is effectively saying that, because FGM does entail such practises.
Also justifications for both FGM and MGM do vary around the world but not without similarities.
All that complicates and confuses the discussion when comparing FGM with MGM. Yet that does not mean they're not comparable.
...the most severe forms of female circumcision rather often do result in a near-total loss of pleasurable sexual sensation, despite the internal structures that may be left intact.
Remember that your original claim was based on prevalence with the important criteria "the majority". What you're discussing now is not the majority but "the most severe forms" i.e. not typical forms and also less prevalent.
Consider that even many uncircumcised women experience difficulty achieving sexual arousal and multiply that by painful vulval and vaginal scarring and female-circumcision-practicing cultures' lifelong inculcations excluding pleasurable sexuality from descriptions of proper femininity (inculcations which have no real functional male equivalents in any culture I'm aware of) and you'll invariably end up with something that by the thinking of any Western culture would constitute catastrophic sexual dysfunction.
I wish you'd be more specific in your terminology, your data, your objective criteria, your reasoning and your claims. In some parts of the world (for example in Sudan) some of the women are subjected to some of the most drastic and horrific forms of FGM. I believe it is these practises you're referring to, but cannot be sure as you are far from clear about it. But if so they're indeed horrible and worst types of FGM, and also drastically affect sexual pleasure.
I don't know which cultures you are referring to, but just for interest here's an example of "female-circumcision-practicing culture" which apparently values female sexual pleasure:
Cleric: Don’t cut too much female genital to avoid sexuality loss
Not in all countries or cultures the justification for FGM is suppression of female sexuality, not even in all Islamic cultures. Not that I support any form of cutting infants without a medical justification.
. But it is weird to be citing the AAP so often, so let's go outside:
