Yes, the free version of this plugin was designed for the USA. I will eventually change this. For now you can edit the “includes/event_register_attendees.php” at around line #274 to change it to whatever you need.
In the premium version, the registration forms can be customized from the WordPress admin.
What conflicts are you getting? Can you be more specific?
I am aware of a function that was recently deprecated in PHP version 5.3, that may cause some deprecated function notices/warnings. I will be releasing an update to fix this shortly.
@eventespresso Not recently active