"We" were not a uniform body of people, but a series of waves of immigrants
And the part of the reason the US is the greatest economy on the planet (and also the world's leading culture, which is also monetizable) is due to immigration.
For example, consider these immigrants: Albert Einstein, I.M. Pei, John Muir, Joseph Pulitzer, Irving Berlin, Ang Lee, Cary Grant, Arnold Schwarzenegger, Eddie Van Halen, Rupert Murdoch, Mikhail Baryshnikov, Pamela Anderson, Dave Matthews, George Soros, Sergey Brin, Alexander Graham Bell, Marcus Goldman (Goldman Sachs), Pierre Omidyar (eBay), Theodore and Milton Deutschmann (Radio Shack), Maxwell Kohl (Kohl's), Daniel Aaron (Comcast), Sol Shenk (Big Lots!), Jerry Yang (Yahoo!), John W. Nordstrom (Nordstrom's), William Colgate (Colgate), Nathan Cummings (Sara Lee), E.I. du Pont, James L. Kraft, Charles Pfizer, William Procter, James Gamble, Andy Bechtolsheim (Sun / Arista Networks), Andy Grove (Intel)....
Those are of course the 1st gen immigrants. Think about how many 2nd and 3rd gen immigrants who are participating in expanding the US economy and culture (like me, for instance).
It's only natural that people who know and are related to each other would want first and foremost to support each other over any other randomly selected set of people.
Personally I don't care about people who theoretically share some kind of artificial division of humanity with me. Nationalism is a dangerous feeling that should be relegated to its proper recreational use. Man-made borders of a country are only means to achieving scalable governance.
I only care about the myself and my family and the things and people that are important to me. That is why the US is such a great and open country where people of all kinds can work together to create amazing economic and cultural growth. That is the American way!
All barriers to economic freedom reduce everyone's potential. Everyone is different, and mathematically we know that if everyone can specialize in what they are most productive at (whether that is management, computer programing, being a nanny, being a house cleaner), total productivity of humanity is maximized.