I thought about using the vidoes I downloaded, which are in mp4 format. I noticed my TV has a USB drive.

I have connected an iPod and an iPad to a TV using the appropriate cables (HDMI is preferable, but it all depends on the TV's input capabilities). Then whatever video is played on the iDevice shows up on the TV.

The cable setup is an all-in-one sort of thing that you can buy at most any place that sells electronics (e.g., Radio Shack, Best Buy, etc.) or on line. One 30-pin or Lightening plug into the iDevice and one to three cables coming out the other end; sometimes there is also a USB cable so you can charge while playing. Runs about $25-$40.

I don't know from experience, but I imagine a similar arrangement exists if you wanted to go directly from your Mac to the TV.

Lots of newer Macs come with built in HDMI output and there is a handy dandy Thunderbolt to HDMI adaptor, or Thunderbolt to VGA all of which generally work pretty well. There are also third party USB 3 video adaptors but I have no experience with them.