Stretched. While you say we should stop having kids, we have. In order to become a sustaining country without the need for immigration, every woman would need to have 4 kids. If everyone had 2 kids the population would be in the negative decline. If everyone had 3 kids they growth would be at zero. 4 kids puts the population in +'s.
Europe, N.A., Japan are in declines and even China (around 2030 their policy of one child is going to backfire with families only going for males, no more females) will start declining.
So the only option is to go to immigration and have a liberal policy on it for the survival of the nation. You restrict immigration you make your country vulnerable in the future because the countries are not sustainable.
Forget about Europe, they're history of ethnocentrism will destroy them again. Neo-fascists have been elected in Italy calling themselves the Falang and in France Szarkozy has ultra right views on immigration. Germany has issues with its Turkish population and the UK's troubles are well known.
Only country that doesn't have these immigration problems is Canada. United States is going to do itself in with the fringe ant- all immigration movement that's taken hold of a sizable amount of the population.