Are there introductory graduate courses for non-American PhD programs in mathematics?
From Oxford's webpage, Broadening Training, 


  Courses should be designed to broaden your knowledge and understanding of the Mathematical Sciences as a whole. They should, by definition, not be directly related to the topic of your dissertation .. 


And it goes on to list where these courses can come from. I took a look at some of the offerings, and as a US graduate, to me they essentially amount to any approved graduate-level course. Whether you can call them introductory is a bit subjective (course looks cool, ends up nightmare, etc.), but they also confirm that part of these 100 hours of broadening does include seminars and colloquia.