Actually, the vast majority of the Irish came before there was an Ellis Island -- and there was almost no way to be an "illegal" as immigration was very lightly controlled. And plenty of them did want to meddle in our politics for the "Old Sod" -- some Irish Union Army veterans tried to conquer Canada to trade it to the brits for Ireland. And they were certainly thought by many to be vast consumers of American services, especially the jails.
Why should we go through that same process again with a group that looks even less promising, in an era of political correctness that makes assimilation impossible?