Who are "Nedivei Am"?
Rashi: They volunteered to be killed for Kidush Hashem.
Radak: The great people of every nation.
Malbim: They volunteered to convert.
Why are they called "Am Elokei Avraham"?
Rashi: He was the first Nediv Lev, the first convert.
Radak: He was the first to make Hashem's name known in the world - "v'Es ha'Nefesh Asher Asu v'Charan", "va'Yikra Sham Avram b'Shem Hashem" (Bereishis 12:5, 13:4).
Who are "Meginei Aretz"?
Rashi: Hashem; He has the ability to be a Magen (shield) for all who trust in Him.
Radak: They are the great people and kings - "Ahavu Hevu Kalon Magineha" (Hoshe'a 4:18).
Malbim: They are all the Tzadikim and Chasidim, who shield the land.
Why does it say "Me'od Na'alah"?
Radak: On that day He will be very elevated over all, and all will admit that kingship is to Him forever.
Malbim: His conduct will constantly be elevated via new miracles and wonders that were not created before.