The U.S. contribution to the WHO amounts to approximately 15% of the organization's annual budget, according to CNN. The claims I see in the right-wing circles are that WHO has little or no actual effect on world health. Hence if the President believes this, then cutting its funding will have little actual detrimental effect on the global health crisis, since it would be consistent with that viewpoint to argue that any actual global effect is being accomplished by some means not affected by the funding. However, effectively cutting its budget by 15% may compel the WHO to take steps that give credibility to the conspiracy the President has offered, that the U.S. response to COVID-19 was delayed by WHO mismanagement. They may, for example, promise to investigate such a "delay" in return for immediate restoration of funding.