How to export 3D plot, without losing the specified view of rotation?

What is stored in variable x is different from rotated object you have in output cell. You rotated - so you changed the properties. Many ways to do this - so in addition to comments' methods...

1) In-Export rotation

2) Seeing options

Export["test.png", Show[x, opts]]

To save a PNG of a plot or graphics expression, I avoid Export. I select the displayed output and click on the Save Selection As ... item on the File menu. This will save the selected output exactly as it appears on the display.