Question: I am a German PhD student in South America and am worried about whether my PhD title will be accepted in Germany (as Dr.) and internationally in general.

If you successfully complete a PhD in the EU, you are allowed to carry the title "Dr.", as any PhD in Germany does.

I am working in a faculty with a professor with international experience, who, for research reasons, left a reasonably strong department in Europe for the position in South America, which is incidentally one of the strongest two departments in South America.

I am attending international conferences every now and then, have two papers published in international journals (one jointly, one alone) and two more papers in preparation.

For all I know, I can reasonably expect that my research performance (and eventually, my PhD thesis) is not below the European standard.

The default format for PhDs from a non-EU country is something like "Hans Wurst (Doutorado, Universidade de Ipanema)", which looks like I should just use my self-confidence instead and not mention that I did a PhD unless someone asks.

I don't know if it's off-topic, because this might just be "too localized", but of course I am wondering if it is possible to have my PhD accredited to use my PhD title in Germany like any "normal" PhD.

I'm also wondering, whether the international community is as strict as German law, or whether I should just call myself "Hans Wurst, PhD" on job applications, my professional webpage, etc. (where the place will be listed somewhere), and hope nobody tells me it should be "Hans Wurst (Doutorado, Universidade de Ipanema)" instead.

Did I make a mistake in my career planning in that the only title that is worth carrying (until full tenure, I guess) I can't carry without a large number of not-so-fancy accessories?

Answer: 
How your PhD is counted depends a lot on from which country you obtained it. Currently, degrees from Australia, Canada, Japan, Israel, and most doctoral-granting American universities are recognized as fully equivalent to "Dr." Beyond that, however, the PhD is listed as a PhD, so long as it's been granted by an institution accredited to give out doctoral degrees. (It has to be legitimately "earned.") You just would not technically be allowed to call yourself "Herr Dr. Hans Wurst"; you'd be "Herr Hans Wurst, Ph.D." (or whatever the formal name of your degree is). 

Unfortunately, the classification of the degree *does* matter in Germany. Someone who holds a *Dr. rer. nat.* (sciences), for instance, will have a harder time getting a position in an engineering faculty than someone who holds a *Dr.-Ing.* (engineering). PhD's may or may not count as being equivalent to either degree, unless the specific regulations of the universities allow for this. (This can make a difference in setting up thesis committees, depending upon the regulations of the faculty in question. Yes, it's really annoying, but that's the way the system is set up.)

Fortunately, as Nate says in his answer, the rest of the world is nowhere near as strict as German law (even the modified version now in effect).

Also, you can apply to the [Zentralstelle für ausländisches Bildungswesen](http://www.kmk.org/zab.html) (Central Authority for Foreign Education) for recognition of a foreign-obtained degree as equivalent to the corresponding German degree.
To address your last question: the international community is *not* as strict as Germany. Here in the US, there are no formal regulations on the use of the title. If you hold an earned doctorate from a reasonable university somewhere in the world, nobody is going to complain about your use of "Dr." or "Ph.D." or both. Even holders of honorary doctorates, or those from non-accredited universities, usually get away with it. On the other hand, we typically don't use those titles as universally as Germans do.