How about removing ships that can't survive a couple hits from a 12" gun?
Should clear off the RN BC quite nicely (just sayin')
How do we define that, then? I'd be glad to, but (for example) are we assuming that the British still have the hokey ammunition handling which OTL was gotten rid off after Jutland?
...and do we also count the OTL post-Jutland refits of the British ships?
I mean, my numbers for ships present are post-Jutland, so there's already three British BCs deleted because they exploded. But looking at the armour thicknesses of the British BCs which did explode:
Invincible
Belt: 4–6 in (102–152 mm)
Decks: 1.5–2.5 in (38–64 mm)
Barbettes: 7 in (178 mm)
Turrets: 7 in (178 mm)
Conning tower: 6–10 in (152–254 mm)
Torpedo bulkheads: 2.5 in (64 mm)
Indefatigable
Belt: 4–6 in (102–152 mm)
Decks: 1.5–2.5 in (38–64 mm)
Barbettes: 7 in (178 mm)
Gun turrets: 7 in (178 mm)
Conning tower: 4–10 in (102–254 mm)
Torpedo bulkheads: 2.5 in (64 mm)
Queen Mary
Belt: 9–4 inches (229–102 mm)
Bulkheads: 4 inches (102 mm)
Barbettes: 9–8 inches (229–203 mm)
Turrets: 9 inches (229 mm)
Decks: 2.5 inches (64 mm)
Conning tower: 10 inches (254 mm)
So if we assume Queen Mary (with the thickest armour of the three which exploded) is the one which defines what can't survive 12" gunfire, then we delete anything with 9" or less main belt or turrets.
This removes all the British BCs.
British 35
German 26
US 15
But it also means we're implicitly assuming that the 12" gun is the smallest valid one, so we should remove any ships with below 12" guns.
Result:
British 35
German 19
US 15
If, on the other hand, we assume that the lighter armour of Invincible and Indefatigable is the "can't survive" level, then that restores three BCs to the British list.
British 38
German 26
US 15
The only definition by which one can consider the US and German fleets combined to be numerically superior to the British is to assume that the British battlecruiser armour level is the level at which things are worthless (hence, to attribute the problems at Jutland entirely to armour instead of to a combination of armour and shell handling), but to still assume that the 11" gun is as effective as the 15" gun and that an 18-knot ship is as effective as a 25-knot ship.
...mind you, here's how many 12" hits the BCs took.
First phase
Lion 9
Princess Royal 6
Queen Mary 3 (+4 11") SUNK
Tiger 0 (+ 14 11")
New Zealand 0 (+ 1 11")
Indefatigable 0 (+ 5 11") SUNK
Second phase
Lion 4
Tiger 0 (+ 1 11")
Third phase
Invincible 5 SUNK
Princess Royal 2
Total 12" hits taken by surviving ships
Lion 13
Princess Royal 8
Tiger 0 (15 11")
New Zealand 0 (1 11")
So Lion and Princess Royal (both Lion class) were able to survive multiple 12" shells. We can thus conclude that their protection was adequate.
Armour:
Belt: 9–4 inches (229–102 mm)
Bulkheads: 4 inches
Barbettes: 9–8 inches (229–203 mm)
Turrets: 9 inches (229 mm)
Decks: 2.5 inches (64 mm)
Conning tower: 10 inches (254 mm)
Tiger has the same level of protection.
The fire at Jutland, though, was long range plunging fire for the most part, so maybe we need to look at deck thickness - and if we do, the SoCals (and many other ships) might need to go as their decks are not very thick at all.
(Actually, that would be interesting but quite a headache.)
You do realize if the US went to war with GB it would start cranking out ships in very large numbers? That the numbers in 1917 at the latest would look nothing like they did in 1912? That the US has more money, more manpower and more ports than GB by a large margin in 1912?
How long are you assuming that the US would take to build their dreadnoughts? I'm assuming that the building program kick-off would be in 1915 at the earliest... the British build times were about as fast as the Brits could make them due to
massive experience, but the US didn't have that much experience and I think they actually had fewer DN building slips.