We  faced another hard argument :p there was like 2 japan subs and a fleet without a sub or destroyer.So we didnt know either the japaneese player could pick up to be submerged or not .İ mean does he have the choice? Althoug it was not his round. İt was American round… Eventually we played  just the first round of the combat. and american fleet fired back. and destroyed the subs.  (Fighters atacked as well ).Did we do something wrong? :s

No, you didn’t. No destroyers present -> Japanese subs have first strike and fire, casualties are removed, then US fires back. AFTER the first turn of combat, subs can submerge if there is no enemy destroyer present. If they are killed though first turn of combat, shit happens. NOTE: This is the Revised rules. In v3 rules (like in Anniversary Edition or so) subs can submerge instantly (there are other differences too).

İs spring 1942 a better game ?  and includes more models or stuff

I admit I am not familiar with Spring 1942, unless it’s the same as the 1942 Anniversary Edition setup. What I can really recommend is the Anniversary Edition (contains 41 and 42 setup), but it’s expensive. The Europe 1940 and Pacific 1940 combine to Global 1940, which seems to be a good but very long game.