When it comes to immigration, people are worried about 4 things.

Wage Reduction for Working Class Americans

Violent Crime and Drug Crime from undocumented immigrants

Undocumented immigrants Not Paying Taxes

1: Wage Stagnation and Unemployment for Working Class Americans

People who are afraid of immigrants will generally agree that immigration is good for the country as a whole. The problem they have is that it harms wages and causes unemployment for working-class Americans who don't have the same opportunities as white collar workers.

The Southern Economics Journal examined the effects of immigration on native-born wages. They determined that undocumented immigrants don't lower wages for the working class. In fact, they found that their wages rose with undocumented immigration. The reason for wage increases is the law of comparative advantage. This law states productivity increases when we have more trading partners.

https://www.forbes.com/sites/artcarden/2015/08/28/how-do-illegal-immigrants-affect-american-workers-the-answer-might-surprise-you/#1da544df771a

University of California, Davis, has written a series of influential papers comparing the labor markets in states with high immigration levels to those with low ones. From 1990 to 2007, undocumented workers increased legal workers’ pay in complementary jobs by up to 10 percent. The one group that has been negatively affected were the unskilled and uneducated. Teenagers still in school as well as high school dropouts. According to the research, the wages of those people were affected by a range between 0.4%, and at worst 7.4%

https://www.nytimes.com/2013/02/17/magazine/do-illegal-immigrants-actually-hurt-the-us-economy.html

https://clas.berkeley.edu/research/immigration-economic-benefits-immigration

A study from David Card at UC Berkeley examined the effects of the influx of immigrants in Miami in 1980. He concluded that only undereducated unskilled workers were affected, but immigration had little to no effect on less skilled workers as a whole.

http://davidcard.berkeley.edu/papers/mariel-impact.pdf

The Economic Policy Institute reached a similar conclusion. They even provided a nifty table on the exact impact of working-class wages over the last few decades. They asserted that wages are technically, but not significantly reduced for unskilled workers overall. They found that the largest contributing factor to wages being reduced for unskilled and undereducated workers is the fact that it is hard for undocumented immigrants to obtain legal status. In their words "any situation where workers’ individual bargaining power is reduced is going to put downward pressure on their wages, and therefore also on the wages of workers in similar occupations and industries." In short, the idea of creating some high barrier to entry is a self-defeating strategy that end's up contributing to wage deprecation for unskilled workers.

https://www.epi.org/publication/immigration-facts/

The numbers vary from study to study but the conclusion is always the same. Immigration, both documented and undocumented have a positive effect on the working class and the poor as a whole. The undereducated are the only group's who's wages are affected but the effects are not terribly significant. Much of the wage depreciation is due to the fact that becoming documented is very difficult. If working-class Americans were truly concerned about the fact that their wages have remained stagnate, they need to look into the effects of Globalization and Automation on wages.

2. Violent Crime and Drug Crime From Undocumented Immigrants.

A study from the University of Wisconson looked at crime rates per state compared to the number of illegal immigrants. Since 1990, undocumented immigration was on the rise but violent crimes as a whole have not correlated. The undocumented immigrant population has tripled. The researchers examined each state independently. Yet the violent crimes rates have been cut in half. The researchers compared crime rates between migrants based on factors that contribute to violent crime ie. unemployment, age, gun availability and drug activity for each of the 50 states. More undocumented immigration meant less violent crime. According to the study, a 1 percent increase in the proportion of the population that is undocumented is associated with 49 fewer violent crimes per 100,000 people. Despite violent illegals being at a disproportionate disadvantage, why are they not creating more crimes? The theory makes sense. Getting to the US and remaining in the US illegally requires plenty of risks and plenty of effort. They simply value their opportunities more because of the effort it took to acquire them.

https://news.wisc.edu/study-shows-undocumented-immigration-doesnt-increase-violent-crime/

Those same researchers also examined nonviolent crime including drug crime. The conclusions were more or less the same.

https://www.documentcloud.org/documents/4450776-Light-Et-Al-AJPH-Published.html

Cato Institute ran a study as well. They isolated their research to the state of Texas. The study found that the violent crime rates were lower than those of native-born Americans. Undocumented immigrants had lower rates of incarceration relative to the population of native-born Americans.

https://www.cato.org/publications/immigration-research-policy-brief/criminal-immigrants-texas-illegal-immigrant

A study done by the University of Texas concluded that illegal immigrants commit less crime than native-born populations.

https://www.chicagotribune.com/suburbs/post-tribune/opinion/ct-ptb-cepeda-immigration-column-st-0506-story.html

Harvard criminologist Robert J. Sampson's study reports that Mexican Americans in Chicago have a much lower rate of violent crime than blacks and whites in the city relative to their population. ?rst-generation immigrants (those born outside the United States) were 45 percent less likely to commit violence than third-generation Americans, adjusting for individual, family, and neighborhood background. Second-generation immigrants were 22 percent less likely to commit violence than the third generation. This pattern held true for non-Hispanic whites and blacks as well. The study also concluded that the areas with the highest population of immigrants have the least amount of crime.

https://www.press.uchicago.edu/ucp/books/book/chicago/G/bo5514383.html

https://contexts.org/articles/sampson/

Another example of a city with high populations of immigrants but lower crime rates is El-Paso Texas. The city is 80% Latino and 26% of its population is foreign-born. In 2011, El Paso had the lowest crime rate of any metro city in the US. Even today, their crime rates remain extremely low for the size of the city.

https://www.texastribune.org/2011/12/08/el-paso-tops-lowest-crime-rate-list-second-time/

3. Undocumented immigrants Not Paying Taxes

Undocumented immigrants not only pay taxes, but it is a net gain for the system. According to the Institute of Taxation and Economic Policy, half of the undocumented workers in the unites states to file for tax returns. Undocumented immigrants paid $23 billion in taxes, but won't receive the benefits. Benefits such as social security, Medicare and income tax credit, and so on. Legal immigrants can't receive the benefits either. Not until they have been in the country for 10 years.

https://itep.org/wp-content/uploads/ITEP-2017-Undocumented-Immigrants-State-and-Local-Contributions.pdf

http://taxpayeradvocate.irs.gov/Media/Default/Documents/2015ARC/ARC15_Volume1_MSP_18_ITIN.pdf

https://www.irs.gov/pub/irs-utl/20-Immigration%20and%20Taxation.pdf