First off, I did *not* "claim that ALL handling characteristics" [emphasis added] derive from the suspension geometry (or as you put it, "the steel frame and general tire placement").
Secondly: Yeah, sure, when you put it that way, that "mere" tuning-type engineering sure sounds like "real" enough engineering...
But in the end, I think you actually prove my original point: You talk about how they "de-tune" cars for the US market; i.e, it's still about "mere" tuning -- OK, not so "mere", that is, as per the above... But still, certainly NOT "nowhere close", AFAICS. I still stand by that point: If not exactly the same thing, they're still quite quite close.