The US will be going back to war as soon as it can find a casus belli. The US Dept of defense is the largest single employer on the planet. Our arms industry is enormous. If there is no war the industry faces the threat of reduced employment and ultimately income.
Aside from that, here's a quote from Biden's speech about Afghanistan I find relevant.
"Today, the terrorist threat has metastasized well beyond Afghanistan: al Shabaab in Somalia, al Qaeda in the Arabian Peninsula, al-Nusra in Syria, ISIS attempting to create a caliphate in Syria and Iraq and establishing affiliates in multiple countries in Africa and Asia. These threats warrant our attention and our resources."