I can only talk from an EU perspective but in my field a junior dev in the US typically starts at the same rate as a senior dev or high end medior dev in NL.

House prices are much lower in the states making buying affordable for middle class families and in some cases even lower class families. This is nearly unheard of in most of europe because of extremely high taxes and significantly lower wages.

Building capital in the US is much easier than it is in Europe because of higher wages, lower taxes and generally cheaper products/services.

Where in the US the economic model is built based on upward mobility and rewarding those who work hard and smart, granted with risks. The EU is mainly running on what is called generational wealth. People who already have lots of money/property keep it regardless of performance while those who do not often don’t. Again there are exceptions to this rule but as a generalization this is true.

The social safety net is better in europe but it comes at a cost. High performers and talented people often get sidelined/punished in the process. The US allows such people to bloom more often at the cost of a stronger social safety net.

It also helps that most major inventions and industries are in the US meaning that getting into the forefront of things is much easier.