You're right -- far too many people take for granted the terrifying ordeal experience on the way to Ellis Island, and then the procedure itself.
These folks got in line like cattle, with NO guarantees, and NO welfare whatsoever -- accepting that the mere opportunity of plying their respective trade and calling America their new home -- and proudly doing so was well worth their blood, sweat and tears.
And again -- these people WANTED to be "Americans."
And people forget that there was land to be homesteaded. Many immigrants came in because the government had a lot of land it wanted settled --- there was so much land -- even the Spanish government passed land grants out to all kinds of people. The land is now all settled, and massive immigration means our huge cities become all the huger --- cities the size of Mexico City --- sprawling slums. Small towns will become big towns and rural life is shut down. The past needs for immigration are gone --- we're no longer trying to be an industrial strength nation --- we've shipped out the jobs that sometimes required immigrant labor.
Anyhow the past is the past --- not much in the past justifies what we do today. Things have changed --- heck --- if we looked at the past for examples --- we could justify going back to slavery --- why pay our dirt cheap labor at all? Why not just buy them from Vicente Fox --- get some new/old kind of commerce going --- breed them, sell them --- that was a form of immigration done in the past --- and for that good old cheap labor reason.