From what I've read the B-17s carried 500lb and 600lb bombs and that is not going to trouble a battleship.
Depends were it hits and the age of the Battleship.
Certainly stories of battleships being hit and shrugging off such hits.
Most of the WW I Battleships had fairly thin decks and turret tops. This was because they expected any shell hits to come in at a fairly flat angle. Max elevation on the main guns was often 15 degrees or under. As battle ranges increased and the elevation went up the angle of decent also went up and required thicker deck armor and turret tops to protect against what was known as "plunging fire". This also increased protection against bombs.
Bombs were also evolving. Stronger bodies to prevent splitting open on impact with hard targets, Better shapes to increase speed (reduce the time of fall) fuses were conastant source of trouble.
On most battleships the "armored deck" was one or two decks down from the open air upper deck. Some ships used 3 different armoured decks to try to disrupt the path of the projectile and get the fuse to function early. Most of the armor was still concentrated in the lower deck as it had to prevent shell fragments from pentraing in the "vitials" and a 12-14in shell had hundreds of pounds of fragments moving at high velocity.
WW I battleships had very few guns without some sort of protection at least this was so after Fisher left office. But with the coming of aircraft the AA guns that began popping up like mushrooms after a good rain filled the deck space with a lot of vulnerable stuff.
In the Washington treaty up to 3,000 tons of extra armor and other "stuff" could be added to existing battleships to modernizem them against aircraft and long range plunging fire.
People are also confusing
sinking the battleship with getting a "mission kill", at what point is the Battleship banged up enough that it has only a small chance of successfully completing it;s mission and needs to return to base for repair. (which may take months). One of the many shades of gray in warfare.
The long range gunnery depended on range finders and directors mount high up on the ship and connected to a center "fire control room" that was often located underneath the main armored deck. While hitting the fire control room was very difficult hitting the range finders and directors was not and could render the "fire control" blind and force a revision to "local" control.
So fire control, secondary batteries, AA batteries, aviation facilities were all vulnerable to bombs that had no hope of killing the battleship out right. They could severely degrade it's combat performance.
Yes 500lb bombs hitting a new or modernized turret roof could bounce off (also means the fuse malfunctioned) but a 500lb hitting close to midships could severely damage AA guns and directors, secondary battery guns & directors, damage main gun fire control equipment and even damage funnels leading to loss of speed due to poor draft through the boiler rooms. Also the bow and stern were seldom protected by the same thickness of armored deck that was used from the fore turret to that aft turret.
It was a constant seesaw between threat and design to counter the threat.
