Why does it say "mi'Merchak"?
Radak: Bavel is far from Eretz Yisrael 1 .
Malbim: A close nation does not destroy [a country that it conquers], rather, it appends it to its border. If it is from far away, it destroys everything and exiles the people.
The Pras river surrounds Bavel on one side (Eruvin 22b), and the slowest Yisrael was able to get from Yerushalayim to the Pras in 14 days (Ta'anis 1:3)! Perhaps Medinas Bavel extended until the Pras, but the [capitol] city Bavel was far away. We find that news of the Churban did not reach Bavel until Teves, five months later (Yechezkel 33:21)!
What is "Eisan"?
Rashi: It is powerful. Radak, Malbim - you cannot fight against them.
What is "Goy me'Olam Hu"?
Rashi: From ancient days it rebelled against Me, in the generation of the dispersion in Eretz Yisrael Shin'ar (Bereishis 11:2-4, i.e. the tower of Bavel).
Radak: It has been a strong nation for a long time. Other nations fear it. Another nation will not help you against it.
Malbim: Do not say that its kingship will not last, and you will be redeemed soon.
What is the significance that they will not understand its language?
Radak: This is more severe than an enemy whose language you understand. Therefore it is among the curses (Devarim 28:49).
Malbim: You will not find grace in its eyes through your Chachmah.
Why does it say "you will not know" and "you will not hear"?
Radak: The matter is repeated in different words.
