Is there a way to change the region on the DVD disc itself?

It's not a matter of region (it's really a TV problem, not a computer problem, but the solution is computers). As the message said, the American PS3 doesn't support PAL. PAL is a different scanning rate than NTSC (the North American standard) and the color information is totally different. (Even if you could get past the scanning rate problem, you'd have a monochrome movie - there's no NTSC color carrier in a PAL video signal.) There ARE, however, PAL to NTSC conversion programs. You'll have to extract the video files from the iso, convert them, make an iso of them and burn that to a blank DVD.