That's location/time I think.
European faeries are little brats. They were made during a time when Nature could kill you a lot easier. Faeries were cold uncaring beasties that would keep you alive one minute and squash you the next for funsies, just like nature would. Your only shield being those small area where man had conquered nature; things like bread and Iron.
American fairies are influenced by baum and are more accommodating being created in a time when there was much industrial progression. Nature couldn't kill you as easy, on the contrary, we were giving nature a swift kick in the ass. So fairies from this place and time are less malicious and are framed as ancient people of the earth trying to protect the earth from us.