It was filmed in California, and anyone familiar with either Maine or California knows it.
If the budget didn't allow on location filming in Maine, they could have just made it the California coast.
Soy 'un hijo de la playa'
That would've changed an awful lot, way beyond simple geography.
East Coast old-money snobbery figured into the plot; so did the fact that living on the island was a hardship for the Hunters: blizzards, treacherous ocean, depressingly short days, isolation. Neither is directly equivalent in California. Lots of contortions to change those two factors from one coast to the other.
And the book had been a bestseller, with the Maine setting important to the story. You lose points with the audience, messing with that.