Q:
Cross Realm transfers EU->NA
A:
Yes, it would affect your ping but prolly not notable.
Anet has servers on different locations. each server (not realm or world!) will have a different ping. NA servers are oprimised for access from NA and EU servers are optimised for acces from EU. but in the end the routing of packets (wich is making the ping time) is being optimised so the difference is getting lower and lower. I doubt if you will experience a real difference.
Arise, ye farmers of all nations
Arise, opressed of Tyria!
Arise, opressed of Tyria!