If you were a US national prior to the new Kenya constitution in 2010, you can regain Kenyan citizenship after jumping through various hoops, if not, then you would never have lost your Kenyan nationality and therefore you are able to apply for your ID and you may then apply for a Kenya passport. Be advised that travelling to Kenya on a Kenyan passport does tie the hands of the US embassy in Kenya in the event of any trouble. My suggestion pay the $50 visa fee at the airport and be done with it.
I don't think there's such a thing as a permanent Visa. I think you want to file the Dual Citizenship. All the forms and instructions are on their website.
Check with the Kenya Government. The Embassy is slow to work with. I only get a recording. Be Blessed Richly
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