How much is non american refundable travel allowance to enter us from nigeria?

As of my last knowledge update in September 2021, Nigerian citizens do not need a non-refundable travel allowance to enter the United States. However, visa regulations and travel requirements can change over time, so it's always best to check with the official sources to confirm the latest information. The U.S. Department of State's Travel Advisory website or the Nigerian Embassy in the United States would be good places to start your research.