You will need a mod chip for your JAP PS2. I've not tried US NTSC games in any way, but JAP originals copy via CDR-WIN and play using the swap trick. modchip.com say that US backups will play with their chip.

PAL originals have to be copied to hard disk, patched (see www.megagames.com) and written back to CD-ROM. Then they play OL using the Swap Trick