On round 2 Japan DoW you only have to defend 3-4 spots. Japan 1 purchased transports -> phil usually. The other 3 boats usually you want to work whatever 3 islands (or 2 islands and malaya).
Then the next round you get the other 2. How people are losing transports is beyond me.
In my last 12 games I have not lost a transport early on. Sometimes spreading the naval to defend against back to back attacks can be tricky. Try to keep fighters on your carriers when this is happening.
Also try to be realistic like say you got a dd sub bship carrier 2 fighter, that should hold against 4 attackers and then 3… that is bare minimal, which is sometimes necessary.
Once you figure out the bare minimal to defend each location and then sprinkle the rest of the naval on it.
Also things like kwangsi or french indo china airbase help to defend against multiple attacks. So sz 36 is usually the safe spot. Usually Japan wants an airbase there because it covers the burma road completely including india, provides reach to critical seazones, and defends naval.
but yeah the allies can win games even without a bid. Just have to take some chances or get lucky early on.