To clarify-

If the US wants to land 2 infantry in the Phillipines with only a transport and the Japanese only have a sub in the sea zone, I cannot land? right?

You used ‘unescorted’ as the operative word.  An unescorted transport cannot amphibious assault a sea zone with an enemy sub.
What if I use a destroyer as an escort… do I need to attack the sub to land? Can I just land without sea combat?  What if the sub destroys my destroyer, can I still land?

Please help!

I keep hearing references to ‘bids’ and I cannot find it anywhere.  Am I missing something?

2nd question-

Say I have a German fighter in Southern Italy.  UK attacks the Italian navy off the coast (no German ships), can the German fighter scramble to protect the Italian fleet?

Thanks!