What reasons did the american party give in the 1840s to encourage immigration reform

The American Party, also known as the "Know Nothings" used the issues of their day to advocate against immigration, specifically the massive influx of Irish and German populations, instead supporting nativism. Their platform was anti-catholic, argued immigrants from Europe should have a longer period of time before being made American citizens and argued these new immigrants were taking jobs from Americans in need. The main goal of the movement was to limit immigration, instead keeping the United States "native" and free of European immigrants. 

Countries of eastern europe.