I don't think it's really fair to compare the US Park Hyatts to the PHT and PHP and saying they're inferior. Of course they would be inferior. Visitors and business people to DC and Chicago aren't going to pay the rates that they can charge in Tokyo or Paris.
Except for a few, I'm sure that the US Park Hyatts aren't selling out on the weekends consistently. They're obviously not targeting the same clientele.
After visiting the PHT, I also believe that it's a cultural issue. I was told that many Japanese stay in hotels not because they are traveling, but for special events. ie "Love Hotels" In the US, I believe that the Park Hyatts are geared more towards business people. Two very different markets and budgets.
There was a survey that showed that Japanese spend an average of ~$160 per night in hotels, where westerners (tourists) spend around $60.