Albert Barnes Commentary Jeremiah 51:49

"As Babylon hath caused the slain of Israel to fall, so at Babylon shall fall the slain of all the land." — Jeremiah 51:49 (ASV)

Render it as: As Babylon caused the slain of Israel to fall, so because of Babylon, have fallen the slain of (or, in) the whole earth. Babylon has to answer for the general carnage caused by its wars.