How would an Iowa-class battleship fare against this kind of beating?

So…a BB is never, ever on its own. Right?

The sinking of Prince of Wales changed things. That was in the opening days of the Pacific war and the British commander badly miscalculated a number of factors. Battleships had not been sunk at sea just by air attack yet at sea. Wiki summarizes the reasons really well.

Yamato should not have been without air cover, either, but the IJN has not been candid with the Emperor concerning how badly it was faring. When Okinawa was invaded, the IJA discussed its plans for the defense and the IJN basically has nothing. When the Emperor asked what they would do, all they could think of was sending Yamato, along with the light cruiser Yahagi and eight destroyers on the suicide mission.

Admiral Ito, the man tasked with commanding the raid, initially objected to the mission, believing it would be futile and meaningless. The captains of the ships sent along also objected, coming close to a mutiny. The believed that a daytime mission without aircover was impossible, and rightfully believed that they would not get close to Okinawa. However, orders from the Emperor were orders and they fell in line.

On what basis do you say that ?

Look, the tests aim to decide if the USS BB can withstand torpedo hits,
not whether the USS BB is better than IJN BB.

Skate fired a spread of four torpedoes at Yamato ; one struck the battleship’s starboard side toward the stern. A hole 5 metres (16 ft) below the top of her anti-torpedo bulge and measuring some 25 metres (82 ft) across was ripped open in the hull, and a joint between the upper and lower armored belts failed, causing the rear turret’s upper magazine to flood…

TDS on Yamato and Iowa is similarly only going to serve to make them difficult to sink. Both Yamato and Iowa class were easily disabled by torpedoes , our attempts to assess how to sink an Iowa is rather speculative but Iowa does have the same compartmentalization concept as Yamato and Titanic… the torpedoes are only getting to the outer compartments right ?