The wave of the first massive immigration from Eastern Europe in 1880-s - see article Three Waves of Massive Polish Immigration coincided with the increase in instability in the USA. This was a time of the industrialization, urbanization and political corruption accompanied by more crime, strikes, prostitution, welfare etc.
For many Americans it was natural to blame immigrants from Southeastern Europe for the increasing problems. Especially since it was a time of the turmoil and increase of racial theories in science after Darvin's evolution theory was published.
This is how the Anglo-Saxon Myth was created. 'Intellectuals like John Fiske, college professors, scientists and others promoted the idea that the process of evolution had culminated in the "Anglo-Saxon race" which was far superior to any other race on the planet. Such thinkers claimed that more "primitive" races (i.e., any "race" that didn't originate in northwestern Europe) did not possess the mental, physical, or social capacities of "Anglo-Saxons." The "Anglo-Saxons" or "Teutons" or "Aryans" were responsible for all the finer points of civilization. "Scientific evidence" of the superiority of the "Anglo-Saxon race" was hardly evidence at all; for instance, some believed the angle of slope on the human forehead was a reliable indicator of human intelligence. "Anglo-Saxons" were more likely to have a high forehead with a more vertical angle of slope than other races; therefore, "scientists" conjectured that "Anglo-Saxons" were necessarily more intelligent.' (Ref. 1). The other were arguing that since Anglo-Saxons were the first to build this country they should protect themselves from the influx of the strangers.
The restrictions on immigration were imposed gradually. In 1882 the law excluded people likely to become public charges. In 1985 the immigration of contract laborer was prohibited (1885). A literacy bill was passed by Congress in 1897, but President Grover Cleveland vetoed it so it was passed again in 1917. The immigrants from outside the Europe were subjected to even worse restrictions than these from Southestern Europe. In 1882 the Congress enacted the Chinese Exclusion Act barring Chinese immigration for 10 years. This act was extended in 1892. According to a Gentlemen's Agreement of 1907-1908, Japan agreed to halt further immigration to the USA but under the condition that the USA would end Japanese discrimination.
The anti-Catholic feelings of the first immigrants did not help Poles in easy assimilation in the USA.For instance according to The American Protective Association 'Catholics "who had started a run on the banks --so the story went-- in order to disrupt the economic system and thus prepare the way for Rome's seizure of power." The speakers of the organization told crowds the unemployed that their jobs had gone to a flood of immigrants unloosened on America by papal agents.' (Ref.2)
"Anti-eastern European feelings (Slavic an Magyar) led to the bloodiest episode in the decade. In 1897, a strike was countered by the police who shot into a crowd of Polish and Hungarian strikers, killing 22 people and wounding forty others. Most American foremen agreed that, if the strikers had been American, no blood would have been spilled. Similar feelings against Italians led to a blood bath in 1895, following violent strikes in the coal fields of Colorado; a group of Italian miners and residents were systematically massacred following the involvement of six Italian workers in the death of an American saloon keeper." (Ref.2)
1. Foreign Immigrants in Industrial America.
2. The period of selective immigration: 1880-1920.