Foreign navies already expected Britain's announced warship program

How would the United States Navy and other foreign navies respond if Britain continued construction?

They already expected Britain to complete its announced program, so continued building would not introduce a surprise expansion.

British construction plans were public enough that foreign navies already expected the ships. The counterfactual continues hulls that had been announced and were already in hand rather than authorizing a surprise expansion. Foreign planners would therefore see earlier delivery of a familiar program, not a sudden change in British intentions. The strategic consequences emerge when those ships become operational, but the procurement signal itself is not new.