If built, the Keystone XL stops in Steele City, Nebraska.
From there, the existing Keystone pipeline sends oil to the Midwest and to Cushing, Oklahoma. At Cushing many different pipeline networks are tied together.
The Gulf Coast pipeline, also owned by TransCanada, is already moving oil at capacity from Cushing to the Gulf Coast. Building the Keystone XL won't change its operations.
based upon http://keystone-xl.com/wp-content/uploads/2014/10/Keystone-overview-booklet-us.pdf
there are two different lines including the Gulf Coast that will have Keystone delivering oil to Texas refineries.
There is zero doubt that Texas will benefit with its plethora of refining capacity.
are you suggesting no effect to Texas from Canadian oil being delivered across the border?