This is literally because the US does not officially recognize Palestine as a sovereign state. If they were to call it Palestine, they would be undermining the government’s stance. That doesn’t mean they agree with it, in fact her slipping on it could be a sign she personally disagrees with the government’s stance. However the feds have never formally recognized it as a state and for them to do so publicly would put their jobs in jeopardy.
Not agreeing with any of it, just wanted to make sure the reason this is happening is clear.