I am beginning to see what you are saying in the OP .
Jeroboam was king , and it was a prosperous period for Israel , and Amos who was not a professional prophet delivered his message from the shrine at Bethel from which Amaziah a priest at Bethel expelled him . He had a vocation from God to speak about judgement resulting from neglect of God’s will , not a popular message hence Amaziah’s wish to be rid of him .
Israel , the chosen nation , cannot be excluded from the will of God . Its phoney clinging to religious practices so as to make them nothing but superstion was condemned , and like all the nations Israel had to be subservient to God’s will , and because it didn’t it would be judged .
The following is a chunk I have copied from the Vatican website on this reading . Its words are much better than mine . - - - - - - - - - - - - - - - -
“This first reading shows us, in the rejection of an Old Testament prophet, what would happen to Jesus and his apostles. For a long time, the territory we call the Holy Land had been divided between a northern kingdom called Israel and a southern kingdom known as Judah. The city of Jerusalem was in Judah. In the northern kingdom, at Bethel, there was a very ancient shrine with several priests. These Bethel priests sponsored the rich people and acted as cronies of King Jeroboam. Amos the prophet was sent by God to these priests with the demand that they speak against the current neglect and exploitation of the poor by the powerful. Amos had come from Tekoa in the southern kingdom of Judah to Bethel in the northern kingdom of Israel, to pronounce God’s judgment on Israel and its King, Jeroboam. As a prophet, Amos foretold the overthrow of the throne and shrine by the hand of God. Amaziah who was the high priest told him that the King was angry with him and he was seeking to kill him. It would be better for Amos to look for his own safety. Amos tells Amaziah that in the eyes of God the Temple that Amaziah served was not legitimate as it had been established by the royal household. But the furious chief priest of Bethel, Amaziah, told Amos to get out and go south to Judah. Amos explained that he was not a professional prophet; he was a shepherd and dresser of sycamores. He had become a prophet only because God had sent him to deliver a message to Israel and its King. We are invited to see the mission of the twelve apostles and our mission as Christians as parallel to the mission of Amos.”