For us in the UK the extent of net immigration from other countries will not directly benefit the economy due to the impact associated with population growth. Our government indicates immigration is a benefit to the economy however a population explosion counter acts this. Regulate the influx of migrant workers, control the borders, monitor and police immigration with enough resources is the way to achieve however reformation of existing laws is the first step in addressing this issue. As I have mentioned this is no easy and quick task and will take significant resources to make it happen. The immigration issue across Europe is much more severe than it is in America especially with it's open borders. The population across Europe is around 500+ million with the UK being the second most densely populated country.
Be aware I am also indicating that immigrants which ever way you want to document their status 'undocumented/illegal' are all good people, I am certainly not implying that. You will have a mixture of people who are willing to go to great lengths to get into a country to work however in order to survive, others to scam the state/businesses and a proportion that will be entering to commit serious crimes and/or become part of gangs/organised crime networks.
Making undocumented immigrants US Citizens is a very upstanding idea but then the population increases, more demand is placed public services, housing, environment, society and the quality of life. This opens up a whole raft of issues relating to the idea of integration of individuals into communities and given they will be classed as poor it they could find they are segregated within society due to their status.
In the US due to the historical and relaxed approach towards undocumented immigration has been the cause of the issue that exists in your country today. The gates are already open and immigration has not been controlled or regulated due to corruption and profit making. For example Walmart was fined $11 million dollars because it employed undocumented immigrants in 2005 and that's a company that was making $285 billion in worldwide sales at the time. So if a large company such as Walmart can exploit immigrants then you can be sure that significantly smaller companies would and will have been doing the same as it made sense for them to exploit cheap labour. US companies hiring illegal immigrants:
http://www.opposingviews.com/i/politics ... rder-fence
http://www.nytimes.com/2014/05/22/busin ... wners.html
http://www.abc57.com/home/top-stories/L ... 22291.html
This is not isolated to the US, it happens over here also:
http://www.theboltonnews.co.uk/news/110 ... s/?ref=mac
In the US when an immigrant produces fake paperwork and an employer turns a blind-eye this can be due to the profits that such a business will make from such individuals. Do you really think that such companies would have cared about reforms being made or increased pressure to employ US citizens? If there are low paid jobs which are not being filled by US citizens and undocumented immigrants are being employed by companies it is because they can exploit these individuals indicates corruption is paramount to make profit. Due to cheaper labour costs, poor working conditions this equates to greater profits for business owners. Immigrants come to work in order to survive and live, corrupt businesses exploit these individuals to make profits. If you factor all the companies that exploit immigrants to make profit then it is no surprise that the reformation of immigration is slow as clearly such businesses will not make the profits that they have been making.
The downside for US citizens is that they do not or will not accept such low paid jobs whereas undocumented immigrants grab these opportunities. The businesses that employ them are aware of this fact which ultimately means they are purposely depressing the wage structure for US citizens. In addition to this those immigrants with fake ID's will not collect social security which then raises the concern where does this go? An immigrant with a fake ID pay's the money in but will never receive as they don't exist but your social security administration receives such deductions from the wages paid. But in order to crack down on this equates to resources and investigations. The US Government has been enforcing fines over the years but not to the extent where is having an impact. This demonstrates lack of commitment, resources and/or willingness to pursue businesses.
A recent news article also appears to indicate that the Government is easing penalties for businesses which hire immigrants which speaks really shows the lack of drive to pursue them:
http://www.washingtontimes.com/news/201 ... /?page=all
So in a way and due to the immoral nature of these business and the fact US Government has turned a blind eye and now won't actively fine them you have in place a modern day slave labour force at work across the US today. Removing it means those businesses will not make the profits they have been making and do you really think they want to make less money in favour of giving US citizens a higher paid job if they can employ low paid undocumented immigrant worker?
Perhaps rather than looking at all the immigrants with disgust and contempt it might be worth focusing this back towards the businesses which are corrupt, the administration that allows immigrants to enter the US in the first place and the fact that the businesses employing undocumented immigrants are not pursued and fined. The immigrants are not free from blame and it is likely they know there very presence in your country will cause issues for everyday Americans. To stop this from happening it needs to be addressed cohesively at the highest levels to the smallest businesses whilst regulating immigration, securing your borders and stamping out corruption associated with profit making.
It's certainly a challenge.
Kren