The Demographic Imperative for immigration

To be a superpower, you have to have a large population.  The reason the United States surpassed the British Empire during WWII is fairly simple.  The US boasted a population in those days of 100 and some million, compared to Britain's 40 million.  That turnover was peaceful due to close historical ties between the two countries and Winston Churchill who clearly saw that an Anglo American alliance, which he succeeded in creating, could win the war and impose a Pax Americana on the world. 
   Lesson to be digested.  To remain a superpower we have to have a large population.  Especially today when we have 320 odd million as opposed to China with a billion, and India with nearly as many.  To maintain our position in the world, we must maintain and grow our population.   And natural increase is failing.  To just maintain a population, to say nothing of growing it, each woman needs to bear 2.1 children in her lifetime.  As of today, America's women are just breaking even, and it looks like they will fall further behind in the coming years.  Continental Europe and Russia are already far behind,  in Russia the figure is down to 1.4 children per woman, and the population of Russia will sink by half in a generation.  Which might explain Vladimir's rambunctiousness on the world stage today.  He wants to get his licks in while Russia still has the population to do it with. 
   America has an advantage here.  We have created the freest, wealthiest, and most pleasant to live in country in the world.  Everyone would like to move here.     We have a tradition of welcoming and assimilating newcomers, the old melting pot idea.  And, immigrants coming from our south are good Catholics and hard workers. Compare with France and Germany, where the immigrants are low grade Islamics who have not  assimilated at all, they are trying to make Europe over into the Middle East. 
   To maintain our population we ought to admit each year, immigrants equal to 1 or 2 percent of the current population.  Say 3 to 6 million immigrants a year.  And since everyone wants to come, we can be picky and admit people who will do the country good.  Young, healthy, loyal, educated, and law abiding we need.  We don't need more elderly, more unemployed, more gang members. 
   We already have a lot (10 million?) of illegal immigrants in the country.  They are picking crops, roofing buildings, waiting tables, probably all for cash under the table.  But, many of them, most of them perhaps, are fitting in, finding work, raising their children to speak English, staying out of trouble with the law, paying taxes.  Which kinda defines a good citizen in my book.  I'm ready to grant to legal papers to good citizens cause we need more good citizens, and in these cases we know who has been good and who hasn't.  I don't really care if they slipped into the country illegally.  Given their circumstances I probably would do the same thing if I had the guts.