This is not restricted to Europe. If we forget about your Mexican immigrants the US has also a birth rate that is frightening low. Espechially those who are reponsible for your unique American culture fail to reproduce themselves. Not that far in the future it is possible that we identify the United States with dark haired muchachas who dance the samba on the streets of Los Angelos.
(BTW - since Mexican girls are among the most beautiful in the world this is not nessecarily a desaster)
That's not to say America doesn't have her problems in this area, but it has not reached the levels here that it has in the old country.