The reason why this is happening is because it is a tab delimited (or other) file that is trying to be opened as a .csv.  Since a .csv is comma delimited file, and a tab separated file contains no commas, excel doesn't know how to delimit the file, hence why everything goes into one column.

Here are the instructions for fixing this (Tested in Excel 2013 & 2010 for both PC & MAx)

1. Highlight all of Column A.

2. Then you Go to the 'DATA' tab.

3. Click 'Text to Columns'.

4. Set Original Data Type is delimited, click Next.

5. Select a 'delimiter' - the most common is "Tab" delimited; if it looks like large spaces between the words, it's tab delimited. Click Next.
         Whatever you have, make sure that box is checked.

6. Column Data format is General, click Finish.