So has America. But the definition of poverty is not absolute positioned, to borrow a CSS analogy. Poverty gets defined relative to wealth. Overall, this is a good thing. But knowing that your poverty is rich compared to the poverty of two generations ago doesn't satisfy humans who gauge their relative social position and are unhappy with it.
Have you ever seen one who was starving? Do they lack access to clean drinking water? Are there malnourished children, without access to schools, begging in America?
Have you ever been to a country where there was extreme poverty?
When people talk about China eliminating extreme poverty, that has a specific international definition. From Wikipedia:
Extreme poverty is the most severe type of poverty, defined by the United Nations (UN) as "a condition characterized by severe deprivation of basic human needs, including food, safe drinking water, sanitation facilities, health, shelter, education and information. It depends not only on income but also on access to services". Historically, other definitions have been proposed within the United Nations.
Extreme poverty mainly refers to an income below the international poverty line of $1.90 per day in 2018 ($2.66 in 2024 dollars), set by the World Bank.[0]
The average homeless person in America spends several times that amount on drugs, and all of the above services are available to them. Homelessness in America is a societal failure, but it does not meet the definition of extreme poverty.