if they do a test on arrival in CDG, it will be a rapid antigen one. And, yes, of course you will need to wait for the results but it is obtained in 15 min. The PCR test you need for Kenya will have to be done in the US before departing. You won’t be allowed to board in IAH if you don’t have everything set up for your final destination.
To come back to your original question, yes this connection is doable. And I doubt the US will go in the next weeks in the red category. They are in the green list now, so if they change, they will likely go to orange before going to red. So the likelihood to get a test on arrival in CDG seems very low to me. And, on top of that, I am not sure that pax in transit are concerned by the tests on arrival.