It would seem as if both Judah and Israel were in view since they both descended from the family of people whom God brought up out of Egypt.1 However, the rest of the oracle focuses especially on the people of Israel, and thus it might be better to understand that God was speaking to Israel rather than Israel and Judah. Of course, since the prophecy was written down, the people of Judah could also learn from these words.
1 Hear this word that the LORD has spoken against you, O people of Israel, against the whole family that I brought up out of the land of Egypt: