Joe Biden's unpopularity began with the withdrawal from Afghanistan

What drives down the president's job approval is the economy, but the Afghanistan fiasco was also a decisive factor.

Month after month the same headline is repeated: Joe Biden's low popularity breaks records. The latest Gallup poll shows that only 38% of Americans approve of his administration. According to the polls, "Between September and June, the president's rating was pegged narrowly between 40% and 43%. Before that, Biden mostly received majority approval ratings."
Citizens' reasons for approving or disapproving of the president usually have to do with domestic issues, and in particular with the economy. But the Axios news portal notes that Joe Biden's abandonment of Afghanistan was a milestone that marked the beginning of the president's decline in the polls.

The impact of the withdrawal from Afghanistan

Thus, Axios notes that "Biden's approval rating was 49% at the start of August 2021, according to Gallup polling. A month later, after the completion of the U.S. withdrawal from Afghanistan, it was 43%. Today, it is 38%."
When asked by Axios, Gallup editor Mohamed Yanounis pointed out that "Historically, what we’ve found is that the economy is always really the driving factor of how Americans rate the president." What's more, "When we ask people, 'What are you going to vote on,' foreign affairs is almost never mentioned."
Now, Younis acknowledges that "The presidential approval rating definitely dipped after Afghanistan, and it’s hard to argue that it had no impact." But neither does he believe that the drop was entirely due to that decision.