For them, that are left in Israel and in Judah - Compare the words in Kings 2 Kings 22:13. in both records the intention is to show that the king regarded the ten tribes as being under his care, no less than the two.
Related Commentaries of 2 Chronicles 34:21
2 Chronicles 34:21
21 Go, enquire of the LORD for me, and for them that are left in Israel and in Judah, concerning the words of the book that is found: for great is the wrath of the LORD that is poured out upon us, because our fathers have not kept the word of the LORD, to do after all that is written in this book.