Controlling how the issue is framed has a larger impact than who wins. Whether APIs are copyrightable is beside the point and no matter who wins, we all lose:
If Google/Oracle can copyright APIs, then they are free to use their market positions to block competition because the very ability to inter-operate with other programs would be infringement, and their monopoly forces everyone to acknowledge their presence.
If Google/Oracle cannot copyright APIS, then they're free to use their market positions to snuff out upstarts by copying / re-implementing their programs.
Whether some method signatures are the same is just evidence suggesting copyright infringement, not infringement itself. I can write a song with some of the same words as another song. That doesn't answer the question of whether that's copyright infringement.