The reason why you don't see homeless immigrants in USA begging in the streets is because there are not too many :))) the majority are not immigrants but temporary residents under H1B visa... In this case if you are laid off you have to get out of US or become illegal which is very unlikely...
Some facts are so horrible but can not be ignored. The news paper "street sense" reported that One third of Homeless pouplation in Toronto area are immigrants. This blog also reports same fact:
http://canadianimmigrationreform.blogspot.com/ Sometimes I wonder that why these scary news only comes from Canada?? Not from US! I don't think that anybody will ever hear the news that Reddy was found near Liberty International Airport, Newark, NJ begging on street instead you might hear that immigrants were involved in multi million dollar insider trading scam. I think that's probably the reason that even Canada welcomes immigrant but people like to wait 10-15 years but to only settle in US