Why are these nations mentioned?
Rashi: They are neighbors of Yisrael. They were punished right after Yisrael, like it says in Yechezkel (25:29-32) and Seder Olam (26).
Radak (24): (a) They did evil to Yisrael. (b) Nebuchadnetzar destroyed these nations. Also he and his seed were stricken in the end, for they harmed Yisrael too much.
Why does it say "Al Egypt v'Al Yehudah..."?
Radak: Melech Ashur already destroyed Yisrael (Malchus Efrayim). Nebuchadnetzar destroyed Yehudah and all the other nations mentioned here.
Who are "Ketzutzei Pe'ah"?
Rashi: This is an expression of the end. They are cast off in the corners of the Midbar.
Radak: They are Kedar and Mamlachos Chatzur, which Nebuchadnetzar struck, like Yirmeyah prophesized (49:28). They dwell in the end, in the corner, i.e. far away in the Midbar. Ketze and Pe'ah are the furthest places on the border.
Malbim (here and 25:23): They are Bnei Keturah and Bnei Yishmael, who cut off the ends of their Orlah (do Bris Milah).
Why does it say "Kol ha'Goyim Arelim..."?
. Radak: Now it explains Mul and b'Orlah in verse 24. Orlah refers to Nochrim, and Mul to Yisrael. Even though their flesh is circumcised, their hearts are Arelim, and they are worthy of punishment. Nochrim are not punished for Orlah, since they are not commanded about it. They are mentioned due to Yisrael, who returned to be like all Arel nations. They are not distinguished from them via their Milah, rather, via their deeds. Since their deeds are like those of Nochrim, and they are Arlei Lev, Milah of their flesh has no benefit. It is as if they did not circumcise. Milas Basar was given for Bris and a sign to be Segulah from all nations to serve Hashem - "li'Vris Olam Lihyos Lecha lEi'lokim ul'Zar'acha Acharecha..." (Bereishis 17:7). There is a sign in their flesh to always remember that they are separate from the nations. Since they mingled with the nations and learned from their deeds, it is as if they annulled the Bris and sign, and they are not lEi'lokim, for they chose in place of Him other gods. Therefore, it says after this "El Derech ha'Goyim Al Tilmedu..." (10:2).
Malbim: Even Bnei Keturah and Bnei Yishmael, who do Bris Milah, are considered Arelim (Nedarim 31b).
