The travel warning issued on September 8 warned US citizens to avoid visits to six counties— Mandera, Wajir and Garissa in the northeast, along with Tana River, Lamu and parts of Kilifi on the Coast.
Nairobi's Eastleigh neighbourhood should also be regarded as a no-go area, the State Department said in that notice.
The notice came on the day the opposition stepped up its push for reforms at the electoral commission before the poll is held.
The National Super Alliance said there will be no election if IEBC official accused of bungling the August 8 poll are not sacked.
It also came a day after President Kenyatta, in his address to Parliament, vowed to maintain peace and ensure the economy is not affected by poll-related chaos.