Even artists from Canada like The Tea Party or from the UK like Texas (yes, *that* popular band in the UK) have a very limited dedicated fanbase. This can only be deeply comprehended when one sets foot in the US. There's a dearth of bands and the competition is very fierce. If you go to these artist showcases like South by Southwest in Austin every spring or the CMJ Music Festival in New York in October, these cities will have a string of clubs booked back-to-back with bands vying for your loyalty and hopefully would eventually land the ever-elusive major label support. Ah, and here's one reason why some deserving Pinoy bands don't have the success they deserve. I hadn't seen any of them give it a shot to participate in these showcases so that some A&R from some label could sign them.
The geographic scope is also very challenging for any touring musician. They'll need an awful lot of capital to cover a land mass that encompasses three time zones. That's why bands like Lokomotiv tend to only keep their coverage within the California area and the odd gig in Chicago or New York. These bands usually have to cough up the money from their own pockets to cover the expenses of their tour. Even bands from the UK embarking on their first US tour seem intimidated by the country's size. To them, slogging it out trekking from North Wales to London can be done within the span of a week or so. That can't be true out here.
Another thing I noticed about most Pinoy-type bands is that they seem to put their ethnicity first and their identity as a musician second. Death Angel, The Pixies, and Versus are examples of bands that made the music do the talking. They only happened to be Pinoys (or have Pinoy band members). I think it's a turn-off for some listeners to deal with identity politics before having to listen to their music.
Aside from that, the average American's "leisure money" also competes with books, films, video games, or even starting their very own band, thus leaving even less time and money to follow another musician's career.