This NPR story shows what the immigration freakout is about. There are fewer (legal) immigrants in the United then there were relative to 1910.
Those immigrants are quite different, however.
The immigrants from 1910 were mainly 87.2% European. Europeans now comprise only 12.3% of the immigrant population. The freakout is that the immigrants of today are not like us, with the gaining countries or regions of origin being Mexico, Asian, Central and South American, and the rest. Both European and Canadian immigration have declined.