Final Cut Pro Apply Transition To All Clips

Yes. Just select the clips and double-click the desired transition; or, if it is the Default transition (which is usually Cross Dissolve, but you can change), just select the clips and press Command-T.

EDIT: and you can do it all from the keyboard: Command-2, Command-A, Command-T

Actually, you can remove all the transitions rather easily, particularly if they are all of the same kind - eg Fade to Color, or Cross Dissolve:

The easiest way to do this is via a wonderful tool that I think is often underused or not used by many people: the Timeline Index.

Open the Timeline Index, and enter some appropriate text in the search box. Here is a quick example:

Just select these transitions here in the index, and press Delete.

Poof!

Cmd-Z for Undo immediately after you do it. Otherwise you have to click and delete each one.

Thank you for the reminder Luis.