The configuration of server aliases for clients is a client configuration rather than a SQL server configuration. As such there's no SQL command to create one, much the same as there is no SQL command to create an ODBC connection.

You can script the configuration using WMI through powershell, the place to start is: http://msdn.microsoft.com/en-us/library/ms179354.aspx and http://msdn.microsoft.com/en-us/library/microsoft.sqlserver.management.smo.wmi.aspx

Here is a powershell example using wmi to create an alias

# List existing aliases
Get-WmiObject -Namespace 'root\Microsoft\SqlServer\ComputerManagement10' -Class 'SqlServerAlias' |
    Format-Table -Property 'AliasName', 'ServerName', 'ProtocolName', 'ConnectionString'

# Example script to create an alias
$alias = ([wmiclass] '\\.\root\Microsoft\SqlServer\ComputerManagement10:SqlServerAlias').CreateInstance()
$alias.AliasName = 'bob'
$alias.ConnectionString = '1433' #connection specific parameters depending on the protocol
$alias.ProtocolName = 'tcp'
$alias.ServerName = 'example_server'
$alias.Put() | Out-Null;

To edit an existing alias, I would do a delete\insert.

I use this PS to delete the alias entries (SQL 2016):

$alias=Get-WmiObject -namespace 'root\Microsoft\SqlServer\ComputerManagement13' -class 'SqlServerAlias' -filter "AliasName='YourAliasName'"
$alias.Delete()