I typed "1975" into Youtube and looked through all 50 pages of results. Here are some videos that I found interesting.
This is some amazing footage shot during the Fall of Saigon. The Fall of Saigon seems to be the most significant event of 1975.
This is really cool. 1975 was three years after the last Apollo mission, when people were still optimistic about NASA and science in general, but interest in the space program was starting to wane.
This reminds me of Ralph Bakshi's "Coonskin" which came out in the same year. They both satirize racist caricatures and stereotypes from old cartoons.
Bakshi's work is probably the only animation made in the 70's which comes close to the quality of cartoons from the 30s to the early 60s.
Most 70s animation looks like this.
Kiss became the biggest band in America in 1975 when they released "Kiss Alive". I'm not a fan, but this footage is great. They look a little less ridiculous in black and white.
This is charmingly uncool.
Footage of the original CBGBs punk bands. In 1975 punk was still an underground movement centered in New York, it exploded the following year.
Here's a collection of trashy B-movies. These were low-budget films made by independent studios. The major studio releases of 1975 are like today's arthouse films - One Flew Over the Cuckoo's Nest, Nashville, and Day of the Locust were among the year's most successful film, and today's big budget, major studio films are like these B-movies - Death Race and Godzilla were both remade as summer blockbusters.
The first summer blockbuster.
Here's some amazing home movie footage. I find 70's home movies really appealing, mainly because they're shot on film.
Here's some videos which I don't have anything to say about.