Why do Americans say Star Trek like Star Track? Is this correct? Because the dictionary says /trek/. I heard several usual Americans say it this way.
When I was six years old, I talked* about this with some of the neighbor kids down the street. They pronounced it "Star Track". I pronounced it "Star Trek". This was in a small town in Wisconsin.
Here's why they pronounced it "Star Track". The word "track" is very familiar, and the word "trek" is not. Indeed none of the neighbor kids knew the word "trek". Even though I loved the show, I did not even know what the word "trek" meant. I just knew from the titles how it was spelled. Even when people hear the name of the show pronounced "trek", they think it's "Star Track" because that sounds like a reasonable name for a TV show about traveling through outer space, since the primary meanings of the word “track” relate to travel: such as footprints and a path along which one travels.
Something similar happened in nursery school a couple years earlier. A girl there consistently addressed me as Bend. We talked about it a bit. She knew the word "bend" but had never heard of the name Ben, so she went with the familiar word. In fact, I started to think that maybe my name was really Bend!
If you're curious to read more about this, search for "priming" in connection with cognitive science and linguistics. Priming explains why people easily mishear an unexpected word as something semantically relevant. I don't know of a term for mishearing an unfamiliar word as a familiar word, but there's plenty of linguistics research about that, too.
American midwest here. I do not pronounce it like "Star Track". In my area we pronounce it like "stahr trehk" where the ah is like "Aha!", the eh is like "Eh.", but this can totally change depending on who you heard say it and where they are from. My grandparents down in Alabama would say it with a southern drawl
"Stahoar Treyk" : try to mash "Stah" and "oar" together into one syllable here.
If you heard someone like my sister from New Jersey say it, they would drop the 'r' sound from star, to get
These are the two accents outside of my own that I'm familiar with.
I've never heard someone (seriously) pronounce it Star Track. If I heard an average adult say it I would assume they were only passingly familiar with the show and messed up the name. If they were a child or otherwise uneducated, I might assume as above that it's because they are unfamiliar with the word 'trek' as opposed to the much more familiar 'track'. In fact, I have heard a child reason out that a 'trek into the wilderness' must be a long trip where they encountered new things and possibly aliens, because they were only familiar with the word as a part of the name 'Star Trek'.
I've heard many black people, including Arsenio Hall, refer to the program as "Star TRACK". Might be that aforementioned familiarity theory. "Trek" is not an everyday word and is probably used even more sparingly in the African American community. You won't often hear:
"I'm gonna TREK on down to da naybahood lickka sto'"