B200,
Actually the rest of the world call it a Bachelor of something. A degree is a degree. Mostly you will find around the world the the first year of college/University is equal to a "Diploma" and if you do two years its an "Associates" Degree. I don't really agree with the two year thing but any more than 2 years and its a Bachelor's either 3 or 4 years. Arts is normally 3 and Engineering usually 4.
The only real difference is in the US as they call the High School qualification a Diploma.
If he wants to join a US major down the track he will need a College/University qualification. Usually a 4 year Bachelor.