Its a dynamic campaign, this would have no repercusions on the story, (so yes- no alternate story line)
But we can start patrolling before pearl harobor takes place, pearl was attacked by carrier launched planes,
SO in theory so long as the carriers are physically where they should be - (and not some kind of invisible entity) we can attack them, but i doubt this will have an effect on ta scripted pearl harbour attack.
I should have been more clear, I ment prevent the attack in the campaign so that physically less planes can take part in the attack, the story would be uneffected of course. Much like the way you can sink the task force that sinks the Bismark in SH3, if youre in the right place at the right time. but the Bismark is still destroyed regardless in the storyline.
Still, im sure we will be able to attack the taskforce and sink some CVs, though it probably wount effect pearl, this would be too much work for the devs.