Amajor cause of antagonism toward the "new immigrants" who came to the united states after 1880 was the belief that they

Americans were afraid that new immigrants would take their jobs during the 1880's. During the late 19th century, the US was constantly expanding by building more railroads, roads, etc. that relied on labor. Businesses often hired the cheapest labor they could since there was no minimum wage laws yet. Often times, immigrants would take a lower pay rate than American citizens.

This fear spread like wildfire and caused an increased amount of nativism. Nativism is the belief that the wants/need of native born citizens should be a priority over those of immigrants.