So much misinformation and so many inaccuracies in your post.
1. Late 19th/early 20th century immigrants came here "legally" in sense that the United States did not have laws barring their entry (with the exception of the Chinese). They weren't forming some orderly queue.
2. Most of those early immigrants crowded in to tenements and worked in sweatshops in large cities. Hardly a skilled labor force.
3. They definitely took over large portions of the country. The upper Midwest today is still dominated by lines of Scandinavian immigrants. Every major city in the East had a Little Italy and a Greektown.
4. The proportion of crimes committed by Hispanics in the US matches closely to their share of the population and their economic status. In fact, studies have shown illegal immigrants are less likely to commit crimes.
5. Hispanic immigrants in the United States learn English. While first-generation Hispanic immigrants do typically have trouble learning the language, 90% of their American-born children are classified as speaking the language "very well" and most of the third-generation can't speak Spanish at all. (Most third-generation Latinos speak English with ease, Pew poll shows | Riverside | PE.com | Southern California News | News for Inland Southern California)
6. Politicians have always pandered to minority communities. Go read about New York City politics in the early 20th century, or even Chicago politics today, where divisions between the Irish, African-Americans, and the Polish still play a big role.
