Yeah I thought this was known - unfortunately the visa situation was really complicated for Pete. Dan and Matt don't need visas, being Americans themselves. As half the band is American, US customs wouldn't treat them as an overseas band, and so wouldn't do a band visa. Hen is on the Haken one, so he's fine, which just left Pete. He would therefore have had to apply for an individual visa, which probably would have taken too long and might not have been successful anyway.
Such a shame it didn't work out. Stupid American immigration systems.