As gower points out, the number of students transferring between medical schools is low; the number of INTERNATIONAL students able to transfer into a US medical school is EXCEEDINGLY LOW.
Why? Well, because schools have several reasons:
1) many do not accept transfers at all
2) some only accept transfers from other LCME schools
3) some only accept transfers when a spot opens up - either due to death, transfer, failing or drop out. These don't happen with any regularity.
4) some schools restrict transfers to state residents
5) some restrict transfers to those with significant ties to the university (ie, family on faculty)
The schools which take the most transfers, particularly international ones, are private colleges of medicine. These are generally very expensive and as an international student, you will be ineligible for US government or bank loans. Thus, many schools may require that you have the full tuition and living expenses for the remainder of the program banked.
There are a couple of books written about transferring. I cannot recall their titles, although one was written by Stanley Z (his last name escapes me, but he writes a great deal of books about USMLE, IMGs, etc.). In addition, you should consider contacting any schools in which you might be interested in transferring into. If you are in a 6 year program in Taiwan, then you would be minimally eligible for transferring after year 4, and after taking the USMLE Step 1. There is no guarantee that the expensive undertaking of applying and interviewing for such a position will result in an offer.
Hope this helps.
------------------
Kimberli "Like a sturgeon" Cox