One of North America's greatest strengths has been its ability to attract immigrants. While some may view the supposed "American Dream" with a great deal of disdain, its hard to deny that most people would still rather immigrate to the US vs China, Russia or even Germany.
People also mistakenly believe that workers from specific countries are simply more industrious or hard working than Americans. I think this is a somewhat flawed assumption. Immigrants are hard working, but are also outliers in their home countries as well. It takes an above average amount of self-confidence, willingness to work hard, and appetite for risk to relocate to a completely foreign country with no friends and few resources. It's the fact that they are willing to immigrate that makes them exceptional, not where they immigrate from.
Incidentally, children of immigrants also have an advantage. Like it or not, we are strongly influenced by the people we spend time with. As a kid, you spend a lot of time with your parents, and you inherit some of their behavior and viewpoints. Children of immigrants are more likely to be scrappy, ambitious and have high risk tolerances. However, this "immigrant mindset" effect seems to fade after a one or two generations.
One thing I've been thinking about lately is how to make sure this "hunger" is passed down without immigrating to a new country. Its also worth noting that this is not a general statement, just an observation I find interesting and have noticed among my friends. For example, extremely wealthy immigrants who enter another country with little personal risk and lots of resources lack the scrappiness and industriousness most commonly associated with the traditional "immigrants mindset".