How credible A-150 intelligence could reshape Allied building

How would the United States and Britain respond to credible A-150 plans and evidence that Japan could build such ships, in the 1939 scenario used for the answer?

The United States would continue its advanced fast-battleship programs, while Britain would have a stronger case to preserve the Lion class and reconsider later King George V hulls.

In the 1939 counterfactual, credible intelligence indicates that Japan can build a class of 20-inch-gun battleships. Iowa is already too far advanced for an easy cancellation or redesign, so the American response emphasizes larger follow-on programs. If Britain receives the information, pausing the Lion class becomes harder to justify. Churchill might instead argue for concentrating on Lions and stopping later King George V hulls, with Anson and Howe proposed for carrier conversion.