Technology exchange did not create common British-American ship designs

When did the Royal Navy and United States Navy begin cooperating on warship design?

They shared technology and experience, especially during the Second World War, but did not generally adopt a common ship-design process.

Britain and the United States exchanged experience and cooperated on particular technologies, especially during and after the Second World War. That exchange did not amount to sustained joint warship design. The two navies continued to make different choices because their design philosophies and operating requirements were not identical. Comparing the ships that emerged is therefore more revealing than assuming alliance automatically produced a common architecture.