Back in the days when all immigrants were welcomed to America, the country was mostly unsettled woods and plains. People could come here, stake a claim to some land, and support themselves with their own farmstead. The reason there are immigration quotas these days is because the systems that make up America in 2011 can't handle large numbers of people outside the sytems moving in and using them. A lot of illegal immigrants get paid cash. They don't pay any taxes on this money. They often have large families, and their children use the tax-funded school systems. The children who are born here are eligible to receive Medicaid, food stamps, and WIC, which are also tax funded. Also, since most of these immigrants don't speak English, places that work with the public have to hire additional workers who speak Spanish in order to work with the immigrant families. Some of the immigrants come from countries that are politically corrupt, and what is considered "normal" behavior is different. Gangs tend to be more common in areas with a lot of illegal immigrants. This increases the burden on police, who are funded by taxes. It's popular to say that illegal immigrants who do pay taxes never get any refunds, but that's incorrect. Illegal immigrants can get a tax ID number and file to get refunds. In addition, they sometimes illegally claim extra children on their tax forms so that they get large refunds. If you think illegal immigrants (from any country) are not a drain on U.S. resources, you are kidding yourself.
Here are some additional things to consider. I know people who lived in nice neighborhoods. When a house came up for sale, someone bought it and rented it out to illegal immigrants. The house became packed with large numbers of people who did not take care of the property. Nearby neighbors managed to sell their houses early on, and those houses ended up being rented out just like the first one. By then, the only way anyone else could sell a house in that neighborhood was to sell it for a big loss.If they didn't do that, they had to stay in the neighborhood, which was like living in a poor Hispanic neighborhood. Those people's formerly nice neighborhood is now full of people who don't speak English, play loud music, have lots of old cars parked every where, keep chickens roaming free, etc. There are often American victims in the immigration wars too.