US is the richest nation in the history of planet earth and the most technologically advanced. It did that by letting markets decide the prices of goods and services.
The fabulously working Soviet economy which didn't believe in market forces and thought a few men in the government knows what millions of producers and consumers should pay each other and how much output to produce. That's why Soviet brands dominated the world economy.
China abandoned the Soviet model in 1978 in favour of markets.
I'm not saying there is no role for the government but the biggest problem in the Chinese economy is there is not enough market forces determining the prices of goods and services. The state owned banks are not lending to SMEs. There is no competition in the financial industry in China. The financial sector is supposed to support the real economy but the Chinese financial system is dominated by state owned banks and the stock and bond market plays a small role in helping SMEs raise funds. Even private banks are a rarity. This means SMEs are starved of funding for their operations. They are at a disadvantage when competing with global companies.
No it isn't. Complete free market economy died by the time 20th century rolled around because people discovered it is a lot closer to anarchism. It also sucked very badly for anything that requires large group effort and coordination, such as modern infrastructure building or war. Most modern day economy is a mixture of both socialist and capitalist economic models.
US' economic success has several historical reason. The biggest one is geography. Like China, US is a nation with greater than 9 million square km of territory and unlike Brazil or Australia, it actually have a lot of fertile land. No offense to Brazilians, but their piece of real estate really isn't the most hospitable place on earth. While the rain forest produce some nature resources, both the output and sustainability is very poor comparing to forest lands in temperate regions. Temperate region forest also becomes decent farm lands after deforestation and it is easy to replant the forest too. The same can't be said about rain forests. Myself was only made aware of this recently, which goes a long way to explain why it is actually Argentina instead of Brazil that flourished in the 50s.
The ocean barrier also meant than the rest of the world setting itself on flame in the two world wars, US received A LOT of capital and technological transfer in form of people fleeing to its safety. Much of US' modern infrastructure is actually constructed when the Federation government has more control. Among engineers, one of the most talked problems today is that after the federal government gradually losing control of the economic, US infrastructure has been slow crumbling instead of improving like many "free market" enthusiasts like to claim.
USSR's problem was never that they don't believe in market force. On the contrary, USSR has a very thorough understanding of economy. (This may be a surprise for a lot of people. Stalin was actually quite proficient at economy and understand both theory and applications very well. Though in retrospect this is not that surprising, this is actually the man who propelled USSR from an agrarian nation to one of the most powerful industrialized nation in the world.) USSR's later day economic problem is the result of several factors:
1. Military overspending: By 80s, USSR has no major allies with US, Europe and China all cooperating to contain USSR. Towards the end of USSR days, a quarter of its GDP is devoted to the defense sector. In comparison, modern US is feeling the strain of military spending and it only devote between 3% to 4% of its GDP to military. Countries like China actually spend only about 1% of its GDP in military spending. This means percentage wise, in one year USSR would spend about two decade worth of military spending of modern day China.
2. Political chaos: After Brezhnev, USSR went through two other leaders very quickly. Historically, any nation would spend its first few decades sorting out leadership and succession chaos. If the nation managed to successfully establish a clean method of leadership transfer in these years, it will go on to last for quite a while. If it fails, then the nation will disintegrate quickly. In modern day China, this can be observed from the rather chaotic transition from Mao Zedong to Hua Guofeng and to Deng Xiaoping. Then The transition from Deng to Jiang is much smoother and Jiang to Hu is smoother still. By the time Xi comes along, Chinese leadership transition has already established a stable and smooth process. US leadership transition is the same thing. The early day of US presidential succession consists of a lot of political struggle, but after a century, the process becomes stable. USSR never managed to reach a stable method of leadership transition and disintegrated as the result. Frankly, this is a way bigger factor in the disintegration of USSR than all other factors combined.
3. Other miscellaneous factors: While we likely to blame Gorbachev's poor decision, the truth is, comparing to the 2nd factor, Gorbachev's blunders are not that significant.