Who abandoned Shomron's Egel?
Rashi: Hashem abandoned you, Bnei Shomron, due to the sin of the calves in Beis Kel 1 that Malchei Shomron served there.
Radak #1: Zanach is distancing, like "Zanach Hashem Mizbecho" (Eichah 2:7). Shomron's calf distanced it. I.e. it distanced Anshei Shomron from their land.
Radak #2: Zanach is Po'el Omed (the action applies only to the subject). It is distanced, like "va'Tiznach mi'Shalom Nafshi" (Eichah 3:17). Shomron ? your Egel is far from you, for it was exiled. When Melech Ashur captured Shomron and Arei Yisrael, he broke the calves and took the gold.
Malbim: This is connected the previous verse. They made idols with their silver and gold in order to cut off the king who abandoned your Egel and did not serve it.
Radak: The calf was in Beis Kel, and not in Shomron. Since the capitol of Malchei Yisrael was Shomron from Achav and onwards, and their kings persisted in Avodas ha'Agalim. It says about each one "va'Yelech b'Chatas Yaravam", "Lo Sar me'Chatas Yaravam" (Melachim II, 13:2, 15:9). Therefore, the Egel is attributed to Shomron. Also the coming verse says "Shevavim Yihyeh Egel Shomron."
Why does it say "Charah Api Bam"?
Malbim: Until now the calves were due to the kings' command. The primary anger was against the kings. Now that the king abandoned the calf, and the people made it from their money, the anger is against the nation.
What is the meaning of "Ad Masai Lo Yuchlu Nikayon"?
Rashi: Until when can they not clear their hearts, to cleanse from that filth?
Radak: Until when (how long) can you not be clean from this sin?!
Malbim: Until when can they not cleanse from the sin of the calves? Now they are not forced to serve them. They have freedom to serve Hashem!
