Powershell: Create stored-procedure on multiple SQL server

Question

Every now and then, I download some scripts (always the same package with more or less the same files in it). I wrote a powershell script that downloads the master.zip, unpacks it, copy the files to a different location and cleans up afterwards.

Now I want to run the .sql files on all my servers, so the servers always have the most actual version on them.

I wrote this powershell script

Function Install-BrentFirstResponderKit
{
    param(
        $server= @("server1","server2")
    )
    $path = "$env:USERPROFILE\AppData\Roaming\Microsoft\SQL Server Management Studio\14.0\Templates\Sql\_Monitoring\Brent"
    $onlyFiles = ("sp_Blitz.sql","sp_BlitzCache.sql","sp_BlitzFirst.sql","sp_BlitzIndex.sql","sp_BlitzLock.sql","sp_BlitzWho.sql", "sp_TEST")
    $files = Get-ChildItem $path\* -Include $onlyFiles

    # Credentials to access SQL-Server
    $credential = Get-Credential -username myadmin -Message "Credentials"
    $username  = $credential.UserName
    $password  = $credential.Password
    $password.MakeReadOnly()
    $creds = New-Object System.Data.SqlClient.SqlCredential($username, $password)

    # Create SQL Connection Object
    $SqlConnection = New-Object System.Data.SqlClient.SqlConnection

    foreach($srv in $server)
    {
        # Open SQL connection
        $SqlConnection.ConnectionString = "Server=$srv; Database=master; Integrated Security=false"
        $SqlConnection.Credential = $creds
        $SqlConnection.Open()

        # Execute SQL Statement 
        $SqlCmd = New-Object System.Data.SqlClient.SqlCommand
        $SqlCmd.CommandTimeout = 0

        foreach($file in $files)
        {
            $SqlCmd.CommandText = Get-Content $file -Raw    
            $SqlCmd.Connection = $SqlConnection
            $sqlcmd.ExecuteScalar()
        }
        $sqlConnection.Close()
    }
}

When I run the powershell script, I get the following error:

Ausnahme beim Aufrufen von "ExecuteScalar" mit 0 Argument(en): "'CREATE/ALTER PROCEDURE' must be the first statement in a query batch." In Zeile:1 Zeichen:1 + $sqlcmd.ExecuteScalar() + ~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : SqlException

Or this error, depending on which file i ran:

Ausnahme beim Aufrufen von "ExecuteScalar" mit 0 Argument(en): "Incorrect syntax near the keyword 'ALTER'. 'CREATE/ALTER PROCEDURE' must be the first statement in a query batch. Incorrect syntax near 'GO'." In Zeile:1 Zeichen:1 + $sqlcmd.ExecuteScalar() + ~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : SqlException

The .sql files are all build in the same way:

IF OBJECT_ID('dbo.sp_TEST') IS NULL
    EXEC ('CREATE PROCEDURE dbo.sp_TEST AS RETURN 0;')
GO

ALTER PROCEDURE dbo.sp_TEST
AS
BEGIN
    Select @@Version
END
GO

While I understand the error-message and found a work-around (remove manually the IF block and remove all the GO messages), it's not what I want.

If I have to edit the files manually (or I could script it with $sqlcmd.SelectCommand = $sqlcmd.SelectCommand.Replace(<if-block>,'')), I could also directly install them manually..

So, my question is, why can't I run a script that starts with anything else than Create/Alter? What am I missing??

Thanks for your help.

PS: I don't know if it would work with Invoke-SqlCmd, but my servers are in different domains and in the past, I had some issues with Invoke-SqlCmd

@Aaron: If I run Get-Content $file -Raw I get the follwing output

IF OBJECT_ID('dbo.sp_TEST') IS NULL
EXEC ('CREATE PROCEDURE dbo.sp_TEST AS RETURN 0;')
GO

ALTER PROCEDURE dbo.sp_TEST
AS
BEGIN
Select @@Version
END
GO

That is exactly the content of $sqlcmd.CommandText

EDIT: As of Dan Guzmans comment, I changed my code to the following and it is now working:

Function Install-BrentFirstResponderKitV2
{
    param(
        [string[]]$server= @("server1","server2")
    )

[System.Reflection.Assembly]::LoadWithPartialName('Microsoft.SqlServer.SMO') | Out-Null

    #alle dateien finden, welche installiert werden sollen
    $path = "$env:USERPROFILE\AppData\Roaming\Microsoft\SQL Server Management Studio\14.0\Templates\Sql\_Monitoring\Brent"
    $onlyFiles = ("sp_Blitz.sql","sp_BlitzCache.sql","sp_BlitzFirst.sql","sp_BlitzIndex.sql","sp_BlitzLock.sql","sp_BlitzWho.sql","sp_TEST.sql")
    $files = Get-ChildItem $path\* -Include $onlyFiles

    # Credentials für den Zugriff auf die SQL Server einlesen
    $credential = Get-Credential -username myadmin -Message "Credentials"

    foreach($srv in $server)
    {
        $x = $sqlConnection = New-Object Microsoft.SqlServer.Management.Smo.Server $srv
        $x.ConnectionContext.LoginSecure = $false
        $x.ConnectionContext.set_Login($credential.username)
        $x.ConnectionContext.set_SecurePassword($credential.password)
        $x.ConnectionContext.Connect()

        foreach($file in $files)
        {
            Invoke-Sqlcmd -Database master -Query $(Get-Content $file -Raw) -ServerInstance $x -Username $credential.UserName -Password $credential.GetNetworkCredential().Password
        }
        $x.ConnectionContext.Disconnect()
    }
}