Why does it say "Nifla'os b'Eretz Cham"?
Radak: Cham was Mitzrayim's father. He is mentioned for detriment (he was cursed). The matter (of verse 21) is repeated in different words.
Malbim: He overrode nature in all of Eretz Cham. The Makos spread through all that pertains to the border of Egypt 1 .
How does he learn from here to all of Eretz Cham? Egypt and Kush argued about the border between them. The Tzfarde'im clarified the border, for they covered Egypt, but not Kush (Shemos Rabah 10:2), even though Kush was Cham's son (Bereishis 10:6)! (PF)
Why does it switch from "Nifla'os" to "Nora'os"?
Radak: Hashem's acts are called Pele. The opposite of nature is called Nora, for via them, Hashem is awesome over people, and they fear Him and admit that He is Master of all, for He reverses nature at His will.
Malbim: He showed Nora'os at the sea, and they feared Him - "va'Yir'u ha'Am Es Hashem" (Shemos 14:31). The verses mention Gedolos, Nifla'os and Nora'os, which correspond to ha'Gadol ha'Gibor veha'Nora. Nora shows that He alone conducts Hashgachah Pratis. "B'Zos Teda Ki Ani Hashem" (ibid., 7:17) is Gedolos; "Ki Ani Hashem b'Kerev ha'Aretz" (ibid., 8:18) is Nifla'os; "Ki Ein Kamoni b'Chol ha'Aretz" (ibid., 9:14) is Nora'os.
