Would other nations join the imperial naval system?

Would more nations join this British naval conglomeration?

No; it remains an imperial/Commonwealth structure, although outsiders may cooperate and the United States may react with earlier battlecruiser construction.

This arrangement is not an open alliance that outside states could simply join. Friendly powers might cooperate, but the staff and fleets emerge from the British Empire's own political transition. A Canada operating battlecruisers could nevertheless prompt the United States to pursue its own battlecruisers earlier, even if American battleships remain individually superior. Compared with this counterfactual, the modern Commonwealth lost much of the intended defense element as Britain prioritized NATO and European commitments, while independent members retained control over their own policy.