Today the Irish are so thoroughly assimilated into the larger American
society that it is difficult for anyone to remember how harshly and
unforgivingly they were greeted as they arrived in the great wave that
began in the mid-1840s and lasted for a decade, but white America
equated them with blacks and stereotyped them accordingly as "childlike
buffoons, lazy, superstitious, given to doubletalk, inflated rhetoric,
and comic misuse of proper English.
White Anglo-Saxons who regarded themselves as "native Americans" gave
the newcomers a frosty welcome. In Boston, employers famously posted
signs that read: "No Irish Need Apply." Irish women, who outnumbered
men, "worked in factories and mills. Irish maids became a fixture of
bourgeois American life. Domestic service became so associated with the
Irish that maids often were referred to generically as ‘Kathleens’ or
‘Bridgets,’ " just as black railroad porters were universally, and
equally patronizingly, called "George."
Thus, often, are attitudes toward poor immigrants from poor countries.
In that age (mid-19th century) before the welfare state, how did these poor, poorly educated, and hated Irish immigrants survive and prosper in America? Involvement in politics was certainly one way. But hardly the only way. According to Yardley, Quinn relates how this "immigrant group" "built its own far-flung network of charitable and educational institutions," and how the Catholic Church also played a major, positive role.
See this earlier post  for references to some important scholarly research on the history of private means of providing charity and mutual aid.