I have been following this thread a bit and may be able to add some material of value.
I am fortunate to have on file a complete set of USN WWII War Damage Reports, including the reports covering most of the cases where USN ships lost or suffered a heavily damaged bow. I also have complete Booklets of General Plans of all or most of these vessels, and in some cases detailed structural plans as well. It would take me several hours -- several days might be more like it -- to go through these again in detail, but I cannot recall any signifiant commentary suggesting that the bow structure in US ships was found to be in any way significantly or typically inadequate, although particularly in the Brooklyn class the structure was quite light. One must remember in that regard, that in many of these cases the torpedoes causing the damage were relatively large, and that in some cases the torpedo hit initiated a magazine explosion of varying magnitude.
The photographs of Belgrano are very similar to other photographs of this class taken during World War II showing similar damage due to similar attacking weapons. The overall appearance of this damage, although spectacular enough to look at, does not immediately suggest any widespread structural deficiencies, although again, as previously noted, the response of the structure does appear to be suggestive of a scheme that is relatively 'light' overall. The general appearance of the damage, however, does suggest a more-than-acceptable level of structural integration. In other words, it's well designed.
Regarding the comparative 'performance' of ships of various nations, about the best general source is Korotkin's "Battle Damage to Surface Ships During World War II". Published in 1960 or so, this work is now somewhat dated, does contain some obvious biases, and does have a tendency to be inaccurate regarding details, but it does represent a rather complete international survey, and is probably fairly reliable so far as the 'big picture' is concerned. Korotkin does note that the loss or substantive collapse of the bows in cruiser-sized vessels (of any nation) attacked with torpedoes hitting relatively far forward would represent the rule rather than the exception, and lists quite a few incidents which are in general support of this finding. Naturally, one would expect light cruisers to do more badly than heavy cruisers, and big torpedoes to do more damage than little torpedoes. Many of the US cases represent light cruisers hit with rather large torpedoes, and substantive collapse or total loss of the bow would, in that regard, hardly be unexpected, or indicative of structural inadequacy. It appears that when the overall picture is taken into account, US cruisers did little worse (and little better) than cruisers of other nations.
There seems to be some sort of relatively unassociated discussion going on regarding the merits of VT fuzes, apparently somehow hooked in to a discussion regarding the efficiency of dual purpose anti-aircraft armament.
In that regard, I think it's well to note that the relative efficiency of the ammunition is only loosely related to the gun installation itself. Certainly it is very hard to make a case that on any given ship a dual purpose secondary armament would represent anything other than a distinct advantage, both tactically and weight-wise, over two sets of single purpose weapons.
Regarding the relative efficiency of time-fuzed and VT fuzed ammunition, this is, again, independent of the details of the guns firing the shells. I have here many thousands of pages of detailed results of USN anti-aircraft test firings prior to World War II. In general, it might be said that these reveal the existence of a rather efficient system, though certainly one which hardly anyone in the USN was happy with. By 1941 or so, it appears that the USN remained somewhat ahead mechanically, but somewhat behind the British operationally; the USN had a better gun system, but the British tended to be -- probably due to having had much more practice -- 'better shots.'
Testing against torpedo planes is difficult to simulate, and it is therefore hard to tell how much better (or worse) a USN dual purpose suite might have done compared to the single-purpose suite on Bismarck. Probably, if for no other reason than the dual purpose system delivered about twice the relative firepower, it would have done better. The quality of the fire control gear would seem to have been relatively unimportant, at least for the Americans, who probably would have employed a successive barrage system in any case. This is not bad. The Germans, if my sense of their procedures is correct, chose the alternative procedure to (try to) get every shell on target. This may, or may not, have been more efficient. Fire control and gun characteristics are important, and sometimes too much control is as bad as too little. When the target is small, unpredictable, and moving fast, a 'good-enough' fire control system with a lot of bullets can sometimes do better than a really good fire control system with a low rate of fire. That's why we hunt ducks using shotguns and not scoped hunting rifles.
The VT 'revolution' would have had a similar impact on any gun system. Tests using VT ammunition are well documented and relatively easy to find. What's interesting is that in many cases a mixed VT and time-fuzed loadout was used throughout the war; When VT ammunition was good, it was very good, but because it didn't go off unless it passed near the target, it often left observers more or less completely in the dark regarding the effectiveness of the fire control solution in use. Time fuzed ammunition, though less likely to knock down the target, created nice puffs of smoke that at least told you roughly where you were.
If someone could make more clear exactly what the VT fuzed discussion is actually about, I might be able to respond more fully.