Now that we have established you're willing to pay to prevent diseases spreading to the US, why do you think that screening at the border is superior to reducing the worldwide incidence, or eradicating them and never having to screen for them ever again?
Border screening clearly has a high failure rate, our recent experiences with this should be fresh in your mind. Besides threatening public health domestically, outbreaks in foreign nations are nevertheless a major economic liability. If COVID had never left China, we would still have seen a huge worldwide disruption, for example.
And anyway, screw them, we got ours is a shit perspective. Empathy should be part of the conversation when talking about so much suffering and death.
If it is clearly personal and you do not have an objective answer then let this be a cause we can choose to donate to based on our personal assessment.
All I can say is, probably not none.
And maybe a note on diminishing returns, in that we might want to reflect on the eradication of smallpox and the near total eradication of polio, and what it has meant to you and to your community to not really have to worry about those diseases.