Great Question!

Assuming that you have already graduated from high school, and are seeking entrance into a postgraduate program in the US, the general rule of thumb is that they are looking for a 3-5 year bachelor’s degree from international students.

Therefore it is unlikely that a Diploma of Business will be accepted as the sole qualification for entrance to a US University for postgraduate studies. Policies, however, vary from school to school so I think it may be worthwhile to ask the schools on a case-by-case basis!