Keep in mind that I am speaking about U.S. education systems. For the best info about studying and working in another country such as Germany or France you'd need to speak with a music educator trained and teaching in that country. If you plan on teaching in a foreign country, for God sakes, know the language and their customs. That being said,
"......However, I do want to study in Europe possibly, and aren't reqs different over there?"
Yes.
The particulars may be different but the basic structure is going to be rather similar. The British have a system of levels.
http://www.rcm.ac.uk/ (I'm sure that there are interent people involved in it that can help you with that far more than I.)
I was told yesterday by a knowledgeable flutist (Jean Baxtresser) that there is more importance put on those Etudes in France. I als think that fundimental European instrumental music teaching puts more emphasis on solfeggio.
http://en.wikipedia.org/wiki/Solfege But again check with the individual university or college music school on your pre-requirements.
"I do plan to take AP Music Theory senior year at my new school."
This type of high school course generally gives the student a basic knowledge that gets them to pass out of a pre mus. theory "materials of music" class.
In my univ., that class is for people without any background in theory. There may be two years of theory on top of that. Music theory can be a stickler for many students because of a lack of pre college experience in it or a lack of basic piano keyboard skills. It can stop them from graduating or delay them from getting out in 4 years. As a warning, even if you are a good student, it may easily take 5 years to graduate in Music Ed. I would still suggest piano lessons for all college music majors and a piano teacher who understands that you are intending this course of study. A good piano teacher who is sensitive to this may be able to teach you some theory such as chords, transposition, modulations, part writing, solfeggio as well as ear training to propare you. I can't stress this preperation part enough.
One other point, If you plan on teaching in a U.S. public school then you'd need to be certified in that state where you are teaching. This would involve taking certain education courses in that state's accredited universities. ~great health care benefits are one incentive to do this. I would guess that on top of your foreign education (although very good) you may need about two years of local accredited study to be certified in any given state. If you get certified in one state and you wish to teach in another, you'd again need some further education to get that state's teaching certification. The specific amount of further study would depend upon each individual state's requirements and is dependent on their need for qualified teachers in general. Calif. for example may be taking any teachers that are able to breathe, have a pulse and that speak some Spanish. Although I'm not so sure about the Spanish or the pulse.
Texas may require a course in Texas history.
~Bilbo
N.E. Ohio