I suppose the USA can isolate itself and take back all it's money, but, the adverse effects of that idea will come to roost.

• The World Health Organization (WHO),(click here) founded in 1948, is a specialized agency of the United Nations with a broad mandate to act as a coordinating authority on international health issues.
• The U.S. government (U.S.) has long been actively engaged with WHO, providing financial and technical support as well as participating in its governance structure.
• The U.S. has been the largest contributor to WHO.
• WHO faces challenges including a broad mandate with limited, inflexible funding, and bureaucratic complexity. It has instituted changes to address prior weaknesses in its health emergencies program, and has played a major role in responding to a number of outbreaks recently.
• WHO is currently helping coordinate a worldwide response to COVID-19, which it declared to be public health emergency of international concern (PHEIC) on January 30, and a global pandemic on March 11, 2020.
• In April, the White House announced it would be suspending financial support for WHO pending a review of the organization’s activities related to the COVID-19 pandemic, with President Trump stating the U.S. contributes “between $400 million and $500 million per year to the WHO.” Assessed contributions from the U.S. to the WHO have ranged from $107 to $119 million over the last decade. The U.S. has also made additional voluntary contributions, ranging from $102 to $401 million per year....
• ...The agency has played a key role in a number of global health achievements, such as the Alma-Ata Declaration on primary health care (1978), the eradication of smallpox (formally recognized in 1980), the Framework Convention on Tobacco Control (adopted in 2003), and the 2005 revision of the International Health Regulations (IHR), an international agreement that outlines roles and responsibilities in preparing for and responding to international health emergencies....
• ...WHO has two primary sources of revenue:
• • assessed contributions (set amounts expected to be paid by member-state governments, scaled by income and population) and
  • voluntary contributions (other funds provided by member states, plus contributions from private organizations and individuals).
  Most assessed contributions are considered “core” funding, meaning they are flexible funds that are often used to cover general expenses and program activities. Voluntary contributions, on the other hand, are often “specified” funds, meaning they are earmarked by donors for certain activities....