If you check out the
sticky thread at the top of this forum you will see the dates that Underworld have announced. I know there are still tickets available for the Dutch gig and for the Luxemburg gig. Not sure about the others. The ticketservice.nl website for the dutch tickets, and the luxemburg ticket ordering sites (atelier.lu) are available in English and they can post the tickets to you internationally. For the Luxemburg gig you can even arrange to pick them up when you get there.
As for asking the question that people have asked and continue to ask without looking for existing threads (which are
here,
here,
here, and
here), there have been no announcements yet.
It is my personal opinion that until they have a product in the stores, that Underworld will not announce something as big as a USA tour. Its far too late in the year to be touring this year so its highly likely that you'll have to wait until next year. If Scott/Yannick want to make me look stupid by announcing dates right after ive pressed the "Submit Reply" button, then I would be happy, just so that I wouldn't have to keep replying to threads regarding a USA tour.