This type exists in American literature, television, and film. Generally speaking, however, happy go-lucky optimists alongside tough authority figures are somewhat more common--think Kaylee and Mal on Firefly. Or, to reverse the genders, Wash and Zoe. (Follow the link for manga examples.) That is, American entertainment tends to favor the active, quippy type. Dreamy heroes or heroines are often entirely dreamy or eccentric--Phoebe on Friends--or savant-like--Cassandra on Librarians.
The dreamy Japanese hero or heroine, however, is almost always non-eccentric as well as quite competent job-wise--despite his or her "quiet spells." Wataru from Only the Ring Finger Knows is a hard-working student. Ryo from Fake is a reliable cop. On the shojo side, artist Kira from Mars is perceived by other students as somewhat more eccentric and savant-like than her male counterparts. Nevertheless, her "normalizing" as Rei's girlfriend is presented as a positive, especially since it doesn't negate her pensive nature.
In other words, the dreamy archetype in Japanese literature is not marketed as outside-the-box for being so reflective and/or spacey. If anything, these characters are portrayed and discussed as utterly ordinary--with a subtle difference. They are normal if interesting. Just like everyone else except . . . The closest American approximation is J.D. from Scrubs who is a capable doctor who just happens to have a vivid fantasy life. So he can go about his day helping people, performing procedures, and making accurate diagnoses while at the same time imagining his bosses as Luke Skywalker and Darth Vadar. (Charlie from Saving Hope is a variation on this plot but not a variation on the archetype--he didn't choose his dreamy side.)
J.D. is perceived as somewhat odd but not in any way eccentric; his behavior is never excused--as is Sheldon's on Big Bang Theory. J.D. is expected--rather like Leonard expects of himself--to conform to the culture around him. And he does...except for all the times he secretly doesn't.
This is quiet, personal, individual rebellion--not big noisy, "look how strange I am" rebellion.
There's a place for both dreamy rebellion and noisy rebellion: Regarding the latter, what would we do without Sherlock Holmes?! (Of course, the Brits seem to have their own version of "I'm not strange--yes, you are--wait, that's not strange" banter.) The pleasure of the dreamy Japanese hero or heroine is one gets to enjoy his or her wandering mind without feeling like the wandering has to make a point. After all, as long as the dreamy hero/heroine don't wander too far, what's the harm?
