Many Republicans, and some Democrats, support the immigration bill because they want to import both high-skilled and so called low-skilled workers rather then pay for training American citizens for the high-skilled jobs and paying a decent wage to American citizens for doing the so called low-skilled work. Meanwhile, the "guilty liberal" faction of the Democratic Party supports an open borders policy basically because they feel guilty for American dominance of the late 20th century and for what they perceive as America's historic misdeeds in the world and they believe that letting in the people of the world is a way of making up for the USA's past transgressions. Another faction of the Democratic Party is the mass immigration faction which, while not supporting completely open borders, supports mass immigration (millions of permanent immigrants per year) for a variety of reasons including those listed above. All of these factions are misguided.
Reliable data indicates that within the next ten years the immigration bill in its current form could result in as many as 50 million permanent and "temporary" immigrants, which would include approximately 34 million permanent residents & citizens. Add this to the nearly 1.5 million natural yearly population increase already existing in the USA and you come up with a yearly population increase of somewhere around 4 to 5 million per year. This puts us clearly on the path to over 1 billion people in the USA by the year 2100. Yes, that's within the lifetime of today's toddlers. See the Census Bureau's own population projections [pdf] or [txt], and when you figure in that we probably already have well over 320 million people when you include the millions of people who intentionally and unintentionally avoided being counted in the most recent census, you'll see that the high immigration levels proposed in the immigration law will put us right on the highest of the four population projections shown in the Census Bureau's projections.
We can have a Pathway to Citizenship and we can also bring in an average of 3 to 4 hundred thousand yearly permanent immigrants and still shoot for keeping our population from never going over half a billion. Remember, the questions to ask the proponents of mass immigration are 1) How many permanent American residents will their proposals lead to and 2) Can the proponents of mass immigration guarantee that there will be enough resources available to Americans to provide all of the people in the United States with at least a middle class quality of life.
The immigration bill is irresponsible in that it would lead to an unacceptable increase of the population of the USA. Most Americans intuitively realize that a billion people is way too many people for the United States. It's time to scrap the immigration bill and to start a new one that includes a Pathway to Citizenship along with provisions that will give American citizens firm control of their borders along with enforceable and strong punishments for employers who illegally hire unauthorized workers in the future (let's not punish the unauthorized workers anymore - their lives are tough enough).
Contact your Senators, your Congressperson and the President and tell them that it's time to rewrite the immigration bill so that it doesn't put the environmental and economic sustainability of the United States at risk.