In Titles & Test, there is a Location drop-down where you can specify exact location of the text box. The first number is the Y-axis. Simply make the Y-number consistent and all titles will be left aligned.
For the record, none of the options are great in Vegas for creating basic PowerPoint style titles and builds. The Legacy titler is the simplest, by choosing Top Left, Center Left or Bottom Left placement.
I have a similar question about Title Builds above.