At a recent event in Washington State, Barack Obama reportedly slammed Donald Trump for his relatively tough stance on illegal immigration. "How many folks here got a little Irish in them?" He also mentioned Italians as a group of immigrants that were met with resistance by many native-born Whites. In so doing, he implied an equivalence between White Irish and White Italian immigration in the 19th century, and the immigration of Mexicans, virtually all of mestizo ancestry, in the 20th and 21st centuries.
There are salient ways in which the two situations are quite different. There are also some ways in which they are the same.
Let's start with the differences. The Irish and the Italians, unlike Mexicans, did not receive affirmative action privileges. During the time in which Irish and Italian immigration levels were high, the federal government of the United States had no welfare programs, with the exception of the oft-forgotten Reconstruction-era Freedmen's Bureau, which was exclusively for Negroes, and therefore not open to poor immigrants from Europe. So the incentives for the immigrants then and now were completely different. The Irish and Italians were incentivized to assimilate and to become more like their native-born neighbors.
By contrast, every incentive is given to Mexican immigrants to maintain a distinct identity from that of Americans. Every Mexican child born in the US represents an increase in the welfare burden to be borne by disproportionately White taxpayers in the future, and increases the pressure put on Whites by the affirmative action privileges given to Hispanics. In addition, while the Irish and the Italians were European, the Mexicans are in large part non-European in ancestry. So the ethnic divide between White Americans and Mexican mestizos is clearly marked out by different racial phenotypes.
Moreover, there is evidence that Mexicans may actually become more criminally-prone in later, US-born generations than in the first generation of immigrants, whereas the Irish and the Italians tended to be less criminally prone in subsequent generations. Finally, there is a real and persistent gap between the average IQs of Hispanics (who are mostly Mexican) and Whites in the US.
What these differences indicate is that the problems with Mexican immigrants will be significantly more durable than problems with Irish and Italian immigrants.
So how is the wave of Mexican immigration similar to those of the Irish and the Italians?
Well, for one, the Mexicans, the Irish, and the Italians all come from groups which are significantly more clannish and less public-spirited than the White Anglo-Saxon Protestant population that formed the ethnic core of the United States at its founding. The Irish practically invented the corrupt "machine" politics that came to dominate many of the US's major cities, from Boston to Chicago. Indeed, they were the first group in the US to organize around explicitly ethnic interests, in opposition to the majority population. The Italians who arrived in the US learned the ropes of this system quite quickly and planted their own flag on the political landscapes of American cities where they formed sizable minorities.
These behaviors weren't limited to the Irish and Italians. Immigrants from Eastern Europe, including Jews, did much the same thing when they arrived in this country in the latter half of the 19th century and the early 20th. This created a significant backlash by the Natives, leading to the Immigration Act of 1924, which sought to stem the ethnic transformation of the United States by imposing national origin quotas, with the intent to ensure that future immigrants would not further alter the demographic makeup of the United States. That the very real problems with the new American ethnic groups reduced in severity to a sufficient degree that they are now considered success stories is in large part due to the cutoff of cultural reinforcements from their homelands in Europe.
The Mexican immigrants of today organize around their ethnic interests much as the European immigrants of the 19th century did. The demographic Mexicanization of the Southwest is promoting an ethnic takeover of the region. As the Mexicans and other Hispanic nationalities grow in numbers, their influence in the US government grows, and the threat of Mexican-style government cronyism becomes more and more present for White Americans further afield.
So in this way, it is true, Mexicans today have important similarities to the Irish, Italians, and other immigrant ethnicities. It's just that the similarities are all bad ones. The ways in which they are different, however, indicate that while the detrimental influences of some of the European immigrants subsided over time, we can expect the detrimental influences of the Mexicans to become more problematic with time.