What gives? I can't afford to travel to these conferences (my department is broke), even if I get a paer into them, and so many of them are not for faculty that it makes me wonder, why the hell can't US faculty put on some freaking interesting conferences? Epistemologically, I love my field of study, but by reading its journals and looking at the other scholars in it, you'd think we're all gutless boors.
I don't know the details of your field, but the likely answer, as it is to most questions, is money. The Euro conferences may be sponsored by institutes that have a budget for it, or they are getting money out of government programs that exist to help sponsor conferences. Additionally, European institutions tend to have larger support staffs than in the US, which soaks up budget but means there are people around to whom the profs fob off the organizational details.
Why don't US faculty put on interesting conferences? Because it requires an amount of organizational gruntwork that is surprising if you've never done it, and there is not much infrastructure to support you.
Or, the opposite can be true on the money end of things: the conferences are low-budget. You don't need to have a big hotel, fancy schmancy catering, special boardrooms, a pricey speaker, and thick programs in glossy folders in order to have a good conference. A good conference is about bringing interesting people together.
I've been to lots of European conferences that have been run for and/or by grad students, and where the operating budget for a two-day conference has been about $800 (made up of 1 or 2 small grants from a funding body or university, and maybe a loan from the department or centre, to be paid back through the conference fees). That amount covers a simple sandwich lunch, photocopying, and wine and chips for an evening reception. Participants pay for other meals, and there is usually an optional conference dinner with a set-price menu worked out ahead of time. Luxurious? Not really. Lots of fun? Often.
Don't see any cool conferences on the menu? Go ahead, organise your own! What's stopping you?