How would an American mage be conceived in Europe? Well, first of all, he should really read up on every country he visits. What wouldn't make anyone so much as pull up an eyebrow in Prague will get you secure arrest in a space prison for life in Britain. Not to even mention the patchwork of weirdo states (*cringes at mere thought*) that once was Germany - if you're awakened, don't go to Westphalia, period. They DO crucify people there, or burn them at the stake. They do that a lot. You have been warned.
Overall, though, Europe has much to offer for maghes of every background.
Hermetics might be best off, for them, Europe offers a lot, be it training and libraries, or access to rare arcane materiel (Prague is the place to be). Though european hermetics (particularily Dr. Faustus Society snobs) could well shun an American for merely coming from a country that hasn't got a four-digit history and for not being up to date with the latest developments in their respective circle (and your hermetic better not be a woman either). The hermeitc in question might enjoy Prague's university - where else can you listen to a Great's lectures about metamagics? I mean, aside from the fact that a 50-feet-long, scaly, horned and winged professor (night black, IIRC) whose teeth are the length of your forearm and whose mere presence fills the lecture hall with a scent of sulfur and burnt meat surely is a pretty intimidating thing to have sitting before you, he's a nice guy, fairly accessible and open to questions (by dragon standards, which means he does expect you top think your every question tthrough fr a month before coming forward with it).
Though Europe's pagan shamanic mages aren't quite as wel organised as hermetics are, they're around too, and fairly common at that (though most are more on the lower social scale). North American shamen will find street witches and wiccans (and followers of the Old Faiths, such as roman, greek, or norse gods) more interesting copmpany. Their traditions aren't too different from themselves - actually, particularily norse 'shamen' tend to follow animal forms as well as idols. Steer clear of funny looking norse worshippers who hate people and use drones a lot, though.