The correct answer to this open question is the following.
Some of the problems that America faced as more and more people emigrated from many different nations were that different people with different background entered the country, they took jobs that supposedly belonged to American citizens, the immigrants did not speak English, and they brought different ideas that were not well accepted by Americans.
This also provoked some defensive reactions from US citizens that did not accept most of the immigrants. Overpopulation of some areas of larger cities also became a considerable problem that affected people. Some of them started to show some signs of racism and indifference to immigrants.
