The one thing we Americans all have in common - except for Native Americans, of course - is the fact we are descended from immigrants. We all came from someplace other than the North American continent. Whether our ancestors came to the U.S. for a better life, investment visa canada to escape political oppression, or embrace religious freedom, once here, they were able to pass on the principle of citizenship to their descendants born on U.S. territory. Jus soli, also known as "right of soil," refers to the automatic and unrestricted right to citizenship by territorial birth. As incredible as the United States is, we earn our inalienable Constitutional Rights simply by being born on U.S. soil.
The 14th Amendment to the Constitution protects the principle of territorial birthright: "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside." Few "advanced economies," as defined by the International Monetary Fund, adhere to the policy of jus soli; but the two major proponents are the U.S. and Canada - both in North America, and therefore considered part of the New World.
Presently, the vast majority of countries in the world use a mixture of both principles when granting and denying citizenship. However, on the other side of the pond, the European Union (EU), comprising 27 countries, has united under a citizenship policy of jus sanguinis ("right of blood"), which recognizes citizenship by descent. Italy refers to its citizenship policy as jure sanguinis or "continuity of blood."
The EU became solidified in regard to its citizenship stance in 2004 when Ireland revoked its automatic right of citizenship solely based on territorial birth. In short, a child born in an EU country is granted citizenship based on the nationality of his or her parents. While France is onboard with jus sanguinis, it still adheres to the principle of jus soli to a certain extent.
The EU's decision to go the way of birthright by blood is based on a number of reasons: the desire to end "citizenship tourism," to curb the influx of asylum seekers, and also to reclaim, to a certain extent, the millions of its citizens who fled their respective countries during various diasporas (large-scale migrations). Ireland and Italy lost millions during the mid-1800s - Ireland due to the Great Famine in the 1840s and Italy due to its unification in 1861. Many of the expatriates found their way to America.
So how does this affect American citizens? It means it's getting easier to obtain dual citizenship, since U.S. citizens can legally hold two passports, and more countries are embracing dual citizenship by descent. According to the U.S. Citizenship and Immigration Services, "The United States does not formally or officially recognize dual citizenship." Nothing can stop a U.S. citizen from applying for dual citizenship, as long as they do not have to renounce their allegiance to the U.S., or take an oath of allegiance to the non-U.S. country.