What is "Goy Chanef"?
Rashi: It is Yisrael.
What is "b'Am Evrasi"?
Radak: This repeats "Goy Chanef" in different words.
Why does it say "Atzavenu"?
Malbim: [Ashur] does not have authority to strike any nation, a Tzadik like a Rasha. I commanded it only "b'Am Evrasi", i.e. Shevet Efrayim, but not on Shevet Yehudah, who are Tzadikim.
Why does it say "ul'Sumo Mirmas [k'Chomer Chutzos]"?
Radak: All will trample on them.
Malbim: Also against the Shevet that sinned, Ashur may not eradicate them, only ["Lishlol Shalal" - to plunder their money,] and trample them like clay, which is proper for building. People trample it to fix it, to make it proper for bricks or earthenware Kelim. So [Ashur] will trample [Efrayim] to fix them and return them in Teshuvah, but not to eradicate them.