As we have learned from Utada's Pheonix interview, she is currently on a Promotional Tour. On the 16th she was in Dallas and Pheonix.
Currently she is in California, and will be on e107.9 The End, a Sacramento radio station, on Weds the 18th in the morning.
They are refering her to as the "Japanese Madonna" - perhaps they heard the Pheonix interview, where Madonna was mentioned while talking about the use of the 'brand name' Utada.
(credit goes to sumiko216 of U-O)

Next, she will be up in San Francisco

UPDATE: [2004/09/06]
Well from the new update to www.Utada.jp, with the new Exodus layout, in the new UTADA section, it lists the USA radio tour as follows:

Apparently her tour was Aug. 15-20, and she went to
Dallas, Pheonix, Sacremento (which we know of already)
but also to LA, San Francisco, Portland, and Seattle!

We wonder if these other radio appearances were broadcasted... or maybe just shelved... if saved for a later date, every one in these cites keep your ears peeled for Utada!