Amos was a shepherd from Tekoa in Israel during King Uzziah (Judah) and Jeroboam (Israel).
Yahweh roars like a lion from Jerusalem. He will not hold back from punishing Syria, Philistia, Tyre, Edom, Ammon, or Moab for their barbarities, especially against Israel.
He will not hold back from punishing Judah, either, for rejecting the Law.
He will not hold back from punishing Israel, either, for her debauchery, though God redeemed Israel from Egypt and brought her into Canaan. She forces her people to disobey the Word. You won't get away from My punishment.
God: I know you, and thus will punish you for your sins. Doesn't God warn His people through His prophets? So I'm warning you. Pieces of Israel will survive, that's it.
This is about Jesus?
Yes. God brought warning to Israel of its destruction through Jesus. He was the one they were to believe in, not just a messenger.
In His Incarnation God showed to us that He knows us.
He is the lion of the tribe of Judah.
We like to hear God's judgment coming on others, and Amos plays to this, pronouncing doom on all the nations around Israel first. But it turns out Israel has become like them, so why should God treat us any differently? It is especially because God knows and chose us to be His special people, that we pursue righteousness and justice. We don't sit back on our laurels in ease and presume on God's grace.