First, IMHO, the Japanese know more about high-speed rail equipment, track, and operation than the various and sundry European and others that claim knowledge thereof will even begin to understand 10 years from now. So, I certainly hope that they stay with the Shinkansen equipment. Another not exactly incidental factor, due t6 the width of the Shinkansen cars, a platform built to give an ADA acceptable gap between platform and car floor will pass AAR standard width freight cars and equipment without need for any special games such as gantlet tracks. (The proper word is gantlet. A gauntlet is an armored glove. A gantlet is a tight passage, usually painful.)
Second, the Texas HSR is in a natural "sweet spot" for distance for a high-speed rail segment. By the time you deal with gate to gate you are essentially equal to rail in time and without the hassles inherent in air travel. Along with this, the terrain and geographt between end points is made for rail. Relatively flat, and without multiple intermediate population center or other major constraints.