Assuming 99% of the users are from the USA, you are correct
In the meanwhile we have dogs with more then 10 generations of European dogs only from many different small countries. Can be hard to find out where each one of them came from.
Am i thinking to high of your brother to create a check box "set/use USA by default" ?
Its not that im to lazy, but im sure if the amount of European users on this database will increase, u will get plenty dogs with the false land of standing, rather then unknown. For the same reason people from USA are not changing unknown to USA.
Anyway, just ideas.