This picture is from the 19th century US periodical Puck. It is saying that the only group in society that will not assimilate are the dreaded Irish (I originally found this and a bunch of other anti-Irish illustrations from the 19th century here).
So here we are, in the 21st century, and of course the dreaded Irish still refuse to assimilate don't they?
What? You mean they have? Gosh. Do you think other cultures and nationalities might eventually assimilate, given time?