Is a Tortillah considered lechem (bread), pas habab'knisin (cake/cracker/pie which assumes the status of bread AIUI when one "makes it a seudah"), or is it a stam mezunos? I haven't seen it explicitly mentioned on the various b'rachos lists.
Are you asking about wheat or corn flour tortillahs?
Wheat flour tortillas are essentially a flat bread, a bit thinner than pitas. ( http://en.wikipedia.org/wiki/Flour_tortilla ) . I see no reason that their bracha should be anything other than HaMotzi as they do not fit into any of the definitions of Pas HaBa'ah B'Kisanin.
Corn flour tortillas are made with corn meal ( http://en.wikipedia.org/wiki/Corn_tortilla ) and like anything made with corn meal (such as corn chips or tortilla chips) their bracha is Shehakol.
I do not have written sources for you on these exact items, but based on basic Hilchos Berachos" these are the correct berachos for these two items.
Concerning corn tortillas, it is also possible for the brachah to be ha-adamah. If the nixtamalized corn is directly made to tortilla rather than processed to flour, the corn kernels would still be recognizable.
As noted on the OU site:
"Say borei pri ha’eitz or borei pri ha’adama for foods made of identifiable pieces of fruit or vegetables.
Note: Even if you know the ingredients in a prepared food–such as grated apples–you must see identifiable pieces in order to say a specific blessing (borei pri ha’eitz, borei pri ha’adama…). If no ingredients are visually identifiable, you must say she’hakol (or possibly borei minei mezonot)." OU.org
See also Kitzur Shulchan Aruch 52:16 And (if I am correct) Seder Birkat Hanehenin 7:23 by the Ba'al HaTanya