Seven points picked up from three group games - including wins against Croatia and Panama - saw England finish on top of Group L, but they were unconvincing in the latter clash, as late goals from Jude Bellingham and Harry Kane sealed a 2-0 victory in New Jersey.
Tuchel has also come into sharp focus for some of his selection decisions both before and during the tournament, after leaving out Trent Alexander-Arnold, Cole Palmer and Phil Foden, with the call on Trent now been questioned again after injuries to right-back pair Reece James and Jarrel Quansah.
The former Chelsea boss has rotated for each game so far, with Ezri Konsa the only member of his back four to start them all, and that's becoming an issue according to Keane.
"The opposition (Panama) were really poor, so we could be critical of England if they didn’t get the job done – but they did. They move on to tougher games. As much as there were pluses from some of the stars, the manager has done lots of chopping and changing.
"I don’t think he has a clue what his best XI is. That’s not good. Defensively, he is chopping and changing."
Keane's comments come as England now focus on their Round of 32 battle with DR Congo on July 1, with Djed Spence expected to cover at right-back, as Konsa remains alongside Manchester City pair Marc Guehi and Nico O'Reilly.