If Japan had attacked the Savo Island transports

Could Japan have won at Guadalcanal by pressing on after Savo Island and sinking the vulnerable American transports?

The landings would suffer, but American replacement capacity would probably recover while Japan's own supply limits remained unchanged.

Destroying the transports after Savo Island would have cost the American landing force supplies and forced another delivery effort. It would still leave the United States able to replace ships, troops, and cargo over time. Japan faced the harder constraint because it could not send enough additional supplies to its own garrison. A much more damaging night action would therefore remain unlikely to produce a straightforward Japanese campaign victory. Industrial and logistical replacement capacity outweigh the immediate tactical success in the longer counterfactual.