I think you're first paragraph is incorrect. For example, the US entered WW2 in 11/7/41, and the BB-63 Missouri was commissioned in 6/44. Missouri saw combat at Iwo Jima and Okinawa. BB-62 (New Jersey) was commissioned in 6/43 and fought at Guam and Okinawa. BB-61 was commissioned 2/43 and fought in the Pacific after being transferred from the Atlantic.
For the UK, five King George class battleships were commissioned after the start of Britain's declaration of war in 9/39. They all saw combat.
France's Richelieu was commissioned in 4/40, and saw limited combat in Dakar.
Even Japan's Yamato class battleships were commissioned before Japan invaded China.
Perhaps you meant that no battleships that weren't laid down prior to the start of WW2 saw combat?
For the UK, five King George class battleships were commissioned after the start of Britain's declaration of war in 9/39. They all saw combat.
France's Richelieu was commissioned in 4/40, and saw limited combat in Dakar.
Even Japan's Yamato class battleships were commissioned before Japan invaded China.
Perhaps you meant that no battleships that weren't laid down prior to the start of WW2 saw combat?