how to get accepted back into a phd program in the US? I was accepted into a US PhD program and then switched to the MSc due to personal reasons. After I got the MSc I wanted to continue to the PhD but then I was told that I have already graduated and was no longer a student there and I should reapply for the following term (spring 2018). So, I could no longer mantain my F1 visa status and had to leave the US.

I have written some emails to the new graduate studies director but they do not repply to me.

I want to reapply but only if I have a good chance to go back. For me it is very expensive and difficult to do so from abroad, especially for the currency exchange rate.

And as far as I know, there are top applicants from Russia and Germany. And I do not know if I will be even considered.

What should I do? How should I approach to the graduate committe?

By the way, I already passed my three PhD qualifying exams. But I stil have no replies to my emails.
The best way to find out if you stand a strong chance of being reaccepted is to get into direct communication with the director of graduate studies or admissions.  (E-mail communication is okay, but talking on the phone would be better.)  That is the person who is best informed about what your chances are.

You may have just gotten a boilerplate answer from a departmental administrator that, since you are no longer a student, you automatically need to re-apply.  While that is undoubtedly true, strictly speaking, it may not be particularly useful information.  The faculty member(s) dealing directly with graduate admissions may be able to tell you a lot more.  Depending on the department, readmission might be a mere formality; or you might be competing on even footing with all the new students who are applying at the same time; or it could be somewhere in between.

If you are intending to continue working under the same advisor you had for your masters thesis, you should contact the advisor as well.  In many departments, if your advisor really wants you, admission can be pretty much guaranteed.  This is especially true if the advisor knows you, has worked with you, and wants you back.