On your MacBook Air, go to Apple menu >> System Settings >> Displays and select the external display.
Apple provides a Use as setting that lets you choose which display is the main display.
You can also select Arrange and relocate the menu bar to the MacBook's built-in display.
Apple describes both options here: Displays settings on Mac – Apple Support and Extend or mirror your Mac desktop across multiple displays – Apple Support. (Apple Support)
If changing the main display has no effect, disconnect the external display, restart the Mac, and reconnect it. Apple notes that display arrangements are retained in macOS, so reconnecting the display can also help determine whether the saved display configuration is involved. (Apple Support)
If the problem remains, your 2022 MacBook Air has Apple silicon. Apple recommends Safe Mode as a diagnostic method for determining whether software that loads during startup is contributing to a problem. Shut down the Mac, hold the power button until Loading startup options appears, select your startup volume, hold Shift, and choose Continue in Safe Mode. Then check whether you can make the MacBook display the main display. Start up your Mac in safe mode – Apple Support (Apple Support)
If the problem also occurs in Safe Mode, I would next check the external display's cable, adapter, or dock and, if possible, test the Mac with another display connection.
Apple provides additional guidance for connecting and configuring external displays here: Connect displays to your Mac – Apple Support.
I would not assume from the timing alone that macOS 27.0.1 caused the problem.
The steps above first establish whether the issue is with the display assignment, the connection, or software loaded during normal startup.