I'd be curious to know what caused that convention to change in the west.
The XBox controller has a swapped A/B pair and uses A confirm B cancel.
When the Playstation 1 was released, the two consoles consumers could have been familiar with in the west were Super Nintendo and Sega Megadrive. SNES had the familiar ABXY, but mirrored with AX on the right. It used A for yes and B for no. The Megadrive had the aforementioned ABCxyz and also used A for yes and B for no. Meaning, one console used the bottom button for yes and the one on its right for no (Megadrive), while the other had the bottom button for no and the one on the right for yes (SNES).
So I doubt SONY copied the competition for their decision to swap the yes/no buttons.
Those of us that grew up with Nintendo consoles would say that B on the left of A is the natural order of things ;)
>Meaning, one console used the bottom button for yes and the one on its right for no (Megadrive)
Actually, almost every Megadrive game I've played lets you use both A and C for accept in menus, so you could use whichever orientation you were more comfortable with.
> I doubt SONY copied the competition
IIRC this wasn't decided by SONY, each game used its own variation until a standard was created organically.
The Genesis' button layout was A,B,C arranged in a diagonal from bottom-left to top-right. A was usually 'accept'. The Dreamcast had a diamond with A at the bottom and B to the right.
Nintendo's Famicom buttons read A,B from right-to-left, and that trend continued with the Super Famicom's diamond, which had A to the right and B at te bottom. The N64 had a weird layout, but again B was to the left of A.
Sony probably focus tested the pad in the US and found that players were more used to Sega's layout.
My guess is that Sony thought that X and O wouldn't have as obvious connotations outside of Japan, and figured that people would assume the button closest to the player (X) would be the OK button. In practice, I have found that people with very little exposure to Japanese culture still have the same association with X and O in their heads and get confused when using Playstations ("you press X to accept???"), so I'll curse Sony forever for this stupid regional change.
That's not to say that those expectations weren't due to cultural differences.
[edited]
example : final fantasy 7 control bindings. http://www.cavesofnarshe.com/ff7/buttons.php