How can I use TransactionScope when making API calls and connectiong to a database in C#?

Question

I am making a number of REST est calls as follows:

using (var scope = new TransactionScope())
{
    try
    {                
        HttpResponseMessage response = MakeRestCall();

        if (response.IsSuccessStatusCode)
        {
            // do stuff;
        }
        else
        {
            throw new Exception("API call not successful");
        }

        response = MakeRestCall2();

        if (response.IsSuccessStatusCode)
        {
            // do stuff;
        }
        else
        {
            throw new Exception("API call not successful");
        }

        MakeDatabaseconnection()
        scope.Complete();
    }
    catch (Exception ex)
    {
        // Handle any exceptions that occurred during the API call
        Console.WriteLine("Exception occurred: " + ex.Message);
        scope.Dispose();
    }
}

private void MakeDatabaseconnection()
{
   string connectionStringTables = "<conn string value>";

   using (SqlConnection connection = new SqlConnection(connectionStringTables))
   {
       connection.Open();  // I get an error here - null reference
   }
}

If I look at connection, it is not null, but the code throws an exception.

How can I make the TransactionScope commit only if all the API calls and the database actions are successful?

Does the procedure MakeDatabaseconnection have to have a dependent scope? If so how can I do that?