I am a citizen of Haiti, currently working in South Africa. I have to travel to Port-au-Prince for family reason. Can I transit to the US? I have B1/B2 visa and will take a covid test prior departure.
No. Foreigners who have been physically present in South Africa in the 14 days before coming to the US are banned from entering the US by Proclamation 10143. You must be able to enter the US in order to transit the US (everyone arriving in the US must immediately enter the US, even if doing an international-to-international transit; the US does not have sterile transit).
You do not fall within any of the listed exceptions. You also do not fall into the exception for H2 workers who have been in South Africa, because you are coming to the US on B2.