A qualitative arms race would reveal practical capital-ship limits

Without treaty limits, which navy would first find the practical size limit for a capital ship?

Probably the United States through a maximum qualitative-race design, although the limit would change as technology advanced.

An unconstrained qualitative race would probably push at least one American program toward a Tillman-style maximum battleship. The resulting design might fail outright or sit just inside the boundary of what yards, machinery, and crews could operate. That experiment would make the practical limit visible to every navy. Improvements in propulsion, armor, and construction could later move the boundary. A practical limit is therefore a technological and industrial condition rather than a timeless tonnage number.