There is another icon there only for the English one -- a file named mailbox_en.tiff. To change your view, rename the original mailbox.tiff to mailbox.tiff.old, make a copy of mailbox_en.tiff and rename it to mailbox.tiff. Restart Mail and then you will have the original amerikan mailbox.
[robg adds: I only run US English, but I have the mailbox.tiff icon in my drawer view; copying and renaming as above didn't have any effect on the displayed icon for me.]

