Depends on the American.
This one (raised in California) says “tube” in a way that could reasonably be spelled “toob”. Of course, I recognize the “tyoob” pronunciation too, but it’s not the one my tongue reaches for first.
Actually, if you’re interested, it’s an example of assonance rather than alliteration.
You’re welcome.
What does “Amazon” have to do with books? Nothing, but it’s memorable and evocative. “Youtube” at least has some connection to the service provided.