Should We Try to stop the new wave of Third World Immigration?

I do not believe that we as Americans should stop the new wave of immigrants from coming into the country and becoming US citizens. It is the cycle of life for America; America was built on the backs of immigrants therefore, that cycle continues. The way people in America survive is that they start from the bottom up. All the immigrants in this nation had to work hard (or oppress another race to work hard for them). So once the immigrants become successful and are accepted as US citizens there are certain jobs the US citizens don’t want to do.
For example lets take a fictional character like Tom who is now a doctor who went to med school at the prestigious Harvard University. Now when Tom was 15 years old he worked at Footlocker as a janitor, so he liked the job when he was young but now that he is 28 and a doctor he would not ever think about going back to being a janitor for Footlocker. Even though there is nothing wrong with a custodial job it is not where Tom saw himself. In this country most people have work from the bottom up. So in this great land of opportunity we are suppose to allow anyone willing to contribute to the success of this country the right to do so. Without immigrants certain jobs some of the people in the country consider tedious and demeaning, will go undone. We should allow “all men the … right to the pursuit of happiness”.