With all due respect, the problem is that most US issuers do not implement the international standard security for online payments that is mandatory in most parts of the world. If you look at the data points, pretty much 99% of failed transactions are with US issued cards - those issued pretty much anywhere else in the world can be processed just fine.

The problem isn't the Kenya eVisa system but rather with your card issuer. They are the ones who need to get their act together and implement the basic 2FA systems that the rest of the world does.