The sentence is grammatically correct as stated; but it means something quite different from what I expect it is intended to mean.
Derive has several meanings, some transitive and some intransitive. In the sentence given here, it is intransitive. The most obvious sense, if we take that at face value, is what linguists do: they derive forms of words or sentence structures from other prehistoric words or underlying sentence structures. (Of course, in the preceding sentence, derive is transitive, with a direct object; but that direct object can be left out—generalising the sentence, you can say that what linguists do is that they derive.)
So taking that at face value, it is perfectly correct to say:
Your English is terrible regardless of where you derive.
In other words, it doesn’t matter where you (who are apparently a linguist) do your derivational work—whether in the office or in the park—your English is still terrible.
This is, of course, a bit far-fetched—who in their right mind would ever find the need to say such a thing?
The more likely sense of the sentence is of course that the speaker thinks the person being criticised has terrible English, and that this is not influenced by where that person comes from.
This is a perfectly understandable, but unusual use of the verb derive. We usually say that things, words, ideas derive from other things or places—they have those other things or places as their source or progenitor. We do not usually say that people derive from other people or places. People tend to originate, hail, descend, or quite simply come or be from (people or) places. Since in this case, I’m guessing the issue is not where the person’s ancestry is, but what country the person is from, hail and especially descend are not good options: they tend to deal with ancestry rather than one’s own life span.
Another problem, which is where the sentence (if taken to mean this, rather than the linguist sense) is actually ungrammatical, rather than just unidiomatic, is that there is a preposition missing. You derive from something; likewise, you originate, hail, descend, or come from somewhere (you can also just originate somewhere, but my gut feeling says that would be more likely to be used of objects than of people).
Therefore, a grammatical and idiomatic version of the sentence—which has the added effect of being simpler, too—would be:
Your English is terrible regardless of where you are/come from.