To work around the problem, you can either:
Method 1: Create two maps. One for the left side, from 0° to 180°, and another for the right side from -180° to 0. Then use the Arrange | Align Objects commands to arrange them so they line up. You should not overlay them, since that will move them back.
Method 2: Add 360 to the X coordinate.
Method 3: Use a file like Pacificp.gsb (attached) to display the base map with positive coordinates from -30 to 360.
Pacificp.gsb base map in MapViewer.
Pacificp.gsb base map in MapViewer converted to Mercator projection.