American fertility has been at or a little below the replacement rate for a generation. Our rate is the highest in the developed world, and our demographic future is generally bright.
Immigrants are the main reason that our fertility rate is near replacement. Immigrants have a somewhat higher fertility rate than the native born. This bump seems to last only one generation, though, so we benefit from continued immigration.
In the recent recession, immigrant fertility fell, and fell even more than native-born fertility. Fertility normally falls during a recession, and bounces back as people become more optimistic about the future. Immigration also fell during the recession, and indeed there seems to have been more return migration to Mexico (at least) than in-migration during that period.
All of which argues to me that the U.S. has a strong interest now in making immigration easy. Likewise, we have a strong interest in making it easier to normalize the condition of migrants already in the country illegally. Moreover, we have an even stronger interest in encouraging the permanent immigration of families, with their higher fertility rates, to insure that we have a sufficient nation - of citizens, as well as merely of workers - in the future.