I too have a US Wii with a Wiikey installed, and through the various forums some time ago, I came across a handy little program called “Wiiscrubber”. All you do is run it, browse to the .ISO of the game and it will tell you the region of the game and if there’s an update included.
You can then select to remove the update, and it does just that. Simply burn the modified .ISO and away you go! The whole process is very fast and so problems so far. Hope it helps.