But legal immigrants do become Americans, as millions have. Gentiles who come to Christ are not illegal.
But now the righteousness of God has been manifested apart from the law, though testified to by the law and the prophets, the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction; all have sinned and are deprived of the glory of God. They are justified freely by his grace through the redemption in Christ Jesus, whom God set forth as an expiation, through faith, by his blood, to prove his righteousness because of the forgiveness of sins previously committed, through the forbearance of God—to prove his righteousness in the present time, that he might be righteous and justify the one who has faith in Jesus. What occasion is there then for boasting? It is ruled out. On what principle, that of works? No, rather on the principle of faith. For we consider that a person is justified by faith apart from works of the law. Does God belong to Jews alone? Does he not belong to Gentiles, too? Yes, also to Gentiles, for God is one and will justify the circumcised on the basis of faith and the uncircumcised through faith. Are we then annulling the law by this faith? Of course not!w On the contrary, we are supporting the law. (Romans 3:21-31)For there is no distinction between Jew and Greek; the same Lord is Lord of all, enriching all who call upon him. (Romans 10:12)
Before faith came, we were held in custody under law, confined for the faith that was to be revealed. Consequently, the law was our disciplinarian for Christ, that we might be justified by faith. But now that faith has come, we are no longer under a disciplinarian. For through faith you are all children of God in Christ Jesus. For all of you who were baptized into Christz have clothed yourselves with Christ. There is neither Jew nor Greek, there is neither slave nor free person, there is not male and female; for you are all one in Christ Jesus. And if you belong to Christ, then you are Abraham’s descendant, heirs according to the promise. (Galatians 3:23-29)
Therefore, remember that at one time you, Gentiles in the flesh, called the uncircumcision by those called the circumcision, which is done in the flesh by human hands, were at that time without Christ, alienated from the community of Israel and strangers to the covenants of promise, without hope and without God in the world. But now in Christ Jesus you who once were far off have become near by the blood of Christ. For he is our peace, he who made both one and broke down the dividing wall of enmity, through his flesh, abolishing the law with its commandments and legal claims, that he might create in himself one new person in place of the two, thus establishing peace, and might reconcile both with God, in one body, through the cross, putting that enmity to death by it. He came and preached peace to you who were far off and peace to those who were near, for through him we both have access in one Spirit to the Father. So then you are no longer strangers and sojourners, but you are fellow citizens with the holy ones and members of the household of God, built upon the foundation of the apostles and prophets, with Christ Jesus himself as the capstone. Through him the whole structure is held together and grows into a temple sacred in the Lord; in him you also are being built together into a dwelling place of God in the Spirit. (Ephesians 2:11-22)
But legal immigrants who go through the naturalization process become American citizens, whose citizenship is not inferior to those who were born citizens. Just like those who are baptized enter into the Church, and are not inferior to those who entered before them.
Consider Romans 11
17And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree; 18Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee. 19Thou wilt say then, The branches were broken off, that I might be graffed in. 20Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear: 21For if God spared not the natural branches, take heed lest he also spare not thee. 22Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off. 23And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again. 24For if thou wert cut out of the olive tree which is wild by nature, and wert graffed contrary to nature into a good olive tree: how much more shall these, which be the natural branches, be graffed into their own olive tree?How else to interpret this, than for it to mean that those who were baptized have been grafted into Israel? And who were the branches that were broken off of Israel, if not those Israelites who rejected Jesus?