When I play as George Washington, my starting Caravel looks like this:

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How do I fix this?

This issue has been raised frequently in the Technical Support forum. See if this helps:

I believe that I have the same problem. One temporary solution I have found is that if you go to the civilopedia from the main menu before loading your game and open a few of the pages for units, the units will appear. This must be done before you load or start a game though. My guess is that it is a problem with loading the unit graphics.