Having more people in our country can only mean a more vibrant economy, more consumers, and better access to labor. Overall a more productive economy and a more productive society(I realize these are sweeping generalization but so be it). Economic growth is fueled by growing markets, growing markets mean we need more consumers or changing consumer demand, we need entrepreneurs taking out loans and taking risks and more immigration can only help those things, be it by shopping at a local super market or opening one, renting a home or building one. (I didn't intend any of this sound condescending and I apologize if you interpreted it in that fashion)
With more people coming into the country, we would have more people working, more people buying things, and more people paying taxes. Contrary to popular belief, the majority of immigrants do contribute positively to our economy. It is only a small minority that are a drain on the system, and that is not something that only immigrants can do.
Although there would be more people for the economy there would be less people working. IT has been proven time and time again. For example WW1 afterwards immigrants took all the jobs of the soldiers who went to fight. When the soldiers returned they returned without jobs. This eventually along with the stock market caused the great depression. We need to get Americans jobs before we get Immigrants Jobs!
No, we already have widespread poverty and homelessness and jobs are tight. Increasing immigration would do little more than increase overcrowding and further limit the wealth available by trying to spread a little around to an ever growing population. We need to look inward first and try to solve the problems with what we have before trying to use outside resources.