Americans began to fear immigrants because of a perception that the immigrants were a threat to American job security. There is a thought that immigrants depress wages, and this affects the American worker.
because of poor economy or war in other countries
Whether American's view of immigrant workers is positive or negative greatly depends on the educational level of the immigrant and what country they are migrating from. In general, the immigrants who draw the greatest ire are those who are unskilled, illegals from Latin American countries.
Would not accept American values.
Neither. The people in power in every country in the Americas are people who are from those countries and the descendants of immigrants. If the question intends to ask about whether in Latin American countries if Indigenous Americans or descendants of Spanish immigrants are the ones ruling the country, the answer is usually that Spanish immigrants or Non-Spanish immigrants are those who rule those countries, primarily because they are the majority and generally better educated. However, several political leaders, like President Evo Morales of Bolivia, are Indigenous Americans.
It changed because they would bring their culture with them
Because the corporations think that immigrants will accept lower pays.
Because of business competition
Nativists believed that fewer immigrants should be allowed in the country because they felt that immigrants took jobs away from native-born Americans, caused social problems, and diluted American culture and values. They also feared that immigrants would not assimilate into American society easily.
To learn English and qualify for American citizenship
This is very opinionated, by American standards yes, because taxes were unfair.
Because of the many immigrants from foreign countries in America.