I assume that public recognition is important to diplomacy and therefore left to the state department to decide.

The State Department (https://www.state.gov/briefings/department-press-briefing-ma...):

  QUESTION: Do Palestinians have a right to self-defense?
  MR PRICE: I’m – in – broadly speaking, Said, we believe in the concept of self-defense. We believe it applies to any state.
  [...]
  QUESTION: Do [you] regard Palestine as a state? [...] You don’t in the context of the ICC and the UN. So are you saying that you do not – if it applies to any state, are you saying the Palestinians don’t have a right to self-defense?
  MR PRICE: I was making a broader point not attached to Israel or the Palestinians in that case.
  QUESTION: So they do have a right to self-defense?
  MR PRICE: I’m not in a position to debate the legalities from up here.