After Kane had given England the lead, Senegal took control to win 1-3 through goals from Ismaila Sarr, Habib Diarra and Cheikh Sabaly.
The 3-1 friendly win was the first time an African nation had defeated England at senior level.
Kane told ITV afterwards: "Not good enough. We had moments, but with and without the ball things aren't clicking, we're not finding the right tempo. We've lost that aggressive nature that we had."
On Jude Bellingham's goal being disallowed, he said: "If you know the rules it's not handball. That gets us back in the game and maybe we can go on and win the game, so it's a big moment. It's something we will discuss later."
On how England can improve, Kane concluded: "We're not going to panic but we know we need to be better. New ideas, there's new players coming into the team that don't have experience at international level. It's a mixture of things but no excuses. We need to find it quick, the World Cup is going to come around really fast so every camp is really important right now."