Very much this.

Different environments result in, over time, different ideologies— humans follow a typical evolutionary path with this, but the adjustments in this case are mental rather than physical.

I love to take risk, but some of my family is from the Soviet Union, and they're extremely risk-averse. Their idea of success in life is to have a stable career as a doctor, lawyer, or engineer.

One ideology isn't inherently better, it's just about which ideology is better suited for which environment. If I were placed in the Soviet Union, I would probably die quickly with my risk tolerance. Meanwhile, while their recipe for conservative success produces solid results in the United States, I would argue that a higher tolerance for risk would produce a better average performance.

The most critical part of this lasting is, of course, what percent of that ideology is inherited rather than questioned... how 'sticky' that culture is, when applied to the immigrant's children. While complex, this is often a function of the closeness of the family unit in that given culture.

This is part of the mythology of the American frontier. Just as America itself was a land of untapped potential for European settlers who had enough of the decadent, stifling old countries of Europe, the West was a land of untapped potential for Americans who had enough of the decadent, stifling East Coast. Just as unpopular New religious sects left for America, the Mormons left for Utah. The gold and silver rushes were outlets for an ambitious American Dream. The verdant fields and valleys of Oregon and California were outlets for ambitions of their own.

The US ran out of frontier around the turn of the 20th century. And this is problematic, because no populations is going to stay as risk-tolerant and ambitious as the population that already risked their lives to travel there in the first place. Immigration might actually refresh these attitudes, but you’d expect them to erode over time. Perhaps they have.

Very true. People wonder why the US is more individualistic and it's a combination of attracting people with that mindset (and repelling people without it) along with people where it's how they grew up.