Superman has, in many ways, become a metaphor for the immigrant experience - someone who came to another place in need of refuge, was accepted by its people, became one of them while using the skills he has as a result of his heritage to help the natives of his adopted world. In recent years, given the socio-politcal and cultural discource around immigration, especially in the United States, this metaphor has become perhaps more relevant than ever.
In a lot of political arguments about Superman, and discussions around this metaphor in particular, I see people bringing up the fact that it was Siegal and Shuster's intention that Superman mirror the immigrant experience.
But is that really true? Was that ever their specific intent?
I mean, if you consider the earliest Superman stories, his alien origin really has ZERO relevance beyond serving as a rationale to explain his powers. In fact, Clark himself was unaware of his Kryptonian heritage for much of the Golden Age, and only discovered the truth in-universe in 1949's Superman # 61...11 years into his existence!
Superman's Kryptonian heritage thus wasn't really a factor in the comics till the 50's. Before that it was confined to the origin story, and even that wasn't recapped as widely as it was in the decades that followed. Superman may have been a household name, but I doubt the origin story was as well-known as it is today.
So is there some other source for this belief that Superman was explicitly intended to be a metaphor for immigration? For instance, interviews with Siegal and Shuster later in life? Conversations they had with people? Notes? Because the stories themselves aren't really concerned with where Superman came from.