You don't need an astronomy undergrad degree at all, as a matter of fact is not expected and from personal experience I can tell you that some advisors will actually advice against it. Why? At this stage you are not really sure if you will go to more traditional areas of astronomy like star structure and evolution or interstellar medium(in that case the astro undergrad is a good idea) or more recent ones like astroparticle physics, early universe cosmology (where a physics degree with optatives like QFT or GR is a better idea). In both cases your decision will hardly affect your chances of admission, again depending on what you want to do it might be a better idea to apply to a physics department.
Regarding the lenguages issue, I don't see any reason why you can't study german and physics while having social life. Unlike some accounts of student's life, it is far from slave labor. Yes, you should work hard but is quite manageable if you are an organized person.
And as far as grad school in Europe goes, I am right now "on the hunt", as far as I can tell you the real good places for astro in Europe (Cambridge, Durham, LMU, Imperial, Oxford, Edinburgh, Heidelberg, Bonn, Potsdam, Padova, Kapteyn, IAC... if anyone knows other ones please tell me!) are as competitive as american schools. Beware of the fees, it can be a real problem if you don't have a financing source. And also note that under the diploma system that is widely spread in continental europe you should finish a masters first. Right now, many countries are adopting the bachelor-master-phd system so it might not apply to you.
Finally I seriously recommend you the mexican option, why? If you are interested in some "traditional" topics like star formation, interstellar medium or observational astronomy (particularly radioastronomy, where Mexican institutes have access to all major facilities and own the biggest millimeter wavelength radiotelescope in the world) the three big mexican institutes (IA and CRyA from UNAM and INAOE) are real powerhouses, admission follows strict admission criteria but is nowhere as hard as other topnotch places, and it's also quite inexpensive to live there.