If you are using Windows joined to Active Directory on your AWS EC2 server and you have configured SSM for it, you can move out of the domain by entering the following commands line by line.
$securePass = ConvertTo-SecureString "******" -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential ("Domain\User", $securePass)
Remove-Computer -Credential $cred -Force -Verbose