Haha Lords of Acid FTW!!!! Disturbed, SOAD, and Slipknot are popular because they make simple, angst-y teen "metal". Ozzfest helped them but that's not why they're famous. They're famous for the same reason Korn and Limp Bizkit became famous: most of the mainstream has shit taste in music. Lacuna Coil are from here and no one likes them because they started pandering to Ozzfest-type bands. Everything after Comalies is shit. They wanted to make more money so they started playing bland, simplistic metal like Disturbed and SOAD and Slipknot (although they're the least worst). It's so funny. When I got here no one really cared about Lacuna Coil because everyone in the metal scene in Milano was like, "Yeah, that's Cristina's band". Now no one really cares about them because everyone in the metal scene here is like, "Yeah, that's Cristina's band that used to write decent music, but then they wanted to play American bro nu-jock metal and so no one cares anymore."
I don't think if NM had played Ozzfest that they would've had the success of bands like Pantera, LoG, Machine Head, etc. Look at all the terrible bands on Ozzfest...Bury Your Dead? Ozzfest didn't help them any. There's a misconception that people make more money touring the US, when in fact many bands LOSE money touring the US if it's not opening for a big headliner like Metallica or on a big festival circuit.
Also, saying that no band has sold a record or a concert ticket in the US for playing all the Euro festivals is just untrue. How do you think metal made its way back to the mainstream in the US? All these Euro bands are able to tour the US simply because of the fans' support for them, and that support came long before they were playing in the US. That support is what made them able to come play in the US. In fact, unless we're talking about big tours and big bands and big festivals, many bands don't like touring the US. It's too expensive, too few dates to justify the time spent traveling, and the promoters often treat smaller bands like crap. Ask Therion how they liked their last US tour. Ask Moonspell as well, while you're at it. All the Euro bands who love touring the states have done it on big tours, not their own small headlining tours or opening up for another small headliner.
Have you ever been to a festival over here? The festivals here are above and beyond festivals like Ozzfest and Mayhem. So many more bands, better promoters, better organizers, etc. I think you're a little out of touch if you think that the US is somehow the golden goose of touring. The 80's and 90's are over. Unless you're on a really big bill or opening for Metallica like Gojira, you're just gonna lose money. There are so many fans in the US and they're plugged into the scene just as much as everyone else, so bands don't need to tour the US on small club shows and lose their hat to be known. Gojira released three albums before setting foot in the US. Malevolent Creation is from Florida and have sworn off touring the US completely.. They only do Euro and South America shows. The reason people want the US market is that it's huge, but breaking into that market is very, very difficult. You have to be willing to either sell out or nearly sell out in order to "sell out" your shows.
Furthermore, a lot of American festivals have terrible lineups. Mayhem has Slipknot, Motorhead, Slayer, and Anthrax as headliners? And the supporting bands are bands like As I Lay Dying and The Devil Wears Prada? Asking Alexandra? BLECH. Those bands would be ONE DAY on ONE STAGE at Wacken, Metalcamp, or Hellfest. Also, you can see by the billing that American music trends play a bigger part in choosing the support bands rather than "passing the torch" or even what the fans really want to see. You have to ask yourself how it is that more American metal bands tour Europe than European bands tour America.