Not so, but nice try. The indicators have nothing to do with race or ethnicity, no matter how you desire to spin that. Plus, USCs aren't what are being looked for, Hispanic or otherwise. The indicators really have little to do with the human being themself, but moreso the mobile conveyance.
Regardless, Suspicionless search is only at an actual border, extended border, or functional equivalent. At these checkpoints, unless the requirements for extended border can be met (not possible with a regular vehicle), then standard PC or warrant requirements of the 4th Amendment apply. No suspicionless search allowed.
On any questions asked, The question was "are you a US citizen", one that takes no more than a second to answer (pointless as the question is), and isn't a kind of incriminating question or one that should necessarily cause anyone to be startled over. Why? Because your answer is taken at face value. You aren't asked for any identification, unless you answer no, which then it would be reasonable to ask for identification. On the one question of immigration, people are creating a problem where there isn't one, and wasting their own time (and everyone else's) when they could be gone and on their way in 2 seconds.
Selected conclusions from U.S. vs Martinez-Fuerte:
"It is agreed that checkpoint stops are "seizures" within the meaning of the Fourth Amendment......
In Brignoni-Ponce, we recognized that Fourth Amendment analysis in this context also must take into account the overall degree of interference with legitimate traffic. 422 U.S. at 422 U. S. 882-883. We concluded there that random roving patrol stops could not be tolerated, because they
"would subject the residents of . . . [border] areas to potentially unlimited interference with their use of the highways, solely at the discretion of Border Patrol officers. . . . [They] could stop motorists at random for questioning, day or night, anywhere within 100 air miles of the 2,000-mile border, on a city street, a busy highway, or a desert road. . . ."
Routine checkpoint stops do not intrude similarly on the motoring public. First, the potential interference with legitimate traffic is minimal. Motorists using these highways are not taken by surprise, as they know, or may obtain knowledge of, the location of the checkpoints, and will not be stopped elsewhere. Second, checkpoint operations both appear to and actually involve less discretionary enforcement activity. The regularized manner in which established checkpoints are operated is visible evidence, reassuring to law-abiding motorists, that the stops are duly authorized and believed to serve the public interest. The location of a fixed checkpoint is not chosen by officers in the field, but by officials responsible for making overall decisions as to the most effective allocation of limited enforcement resources. We may assume that such officials will be unlikely to locate a checkpoint where it bears arbitrarily or oppressively on motorists as a class. And since field officers may stop only those cars passing the checkpoint, there is less room for abusive or harassing stops of individuals than there was in the case of roving patrol stops. Moreover, a claim that a particular exercise of discretion in locating or operating a checkpoint is unreasonable is subject to post-stop judicial review.
The defendants arrested at the San Clemente checkpoint suggest that its operation involves a significant extra element of intrusiveness in that only a small percentage of cars are referred to the secondary inspection area, thereby "stigmatizing" those diverted and reducing the assurances provided by equal treatment of all motorists. We think defendants overstate the consequences. Referrals are made for the sole purpose of conducting a routine and limited inquiry into residence status that cannot feasibly be made of every motorist where the traffic is heavy. The objective intrusion of the stop and inquiry thus remains minimal. Selective referral may involve some annoyance, but it remains true that the stops should not be frightening or offensive, because of their public and relatively routine nature. Moreover, selective referrals -- rather than questioning the occupants of every car -- tend to advance some Fourth Amendment interests by minimizing the intrusion on the general motoring public.
As we have noted earlier, one's expectation of privacy in an automobile and of freedom in its operation are significantly different from the traditional expectation of privacy and freedom in one's residence. And the reasonableness of the procedures followed in making these checkpoint stops makes the resulting intrusion on the interests of motorists minimal. On the other hand, the purpose of the stops is legitimate and in the public interest, and the need for this enforcement technique is demonstrated by the records in the cases before us.
Accordingly, we hold that the stops and questioning at issue may be made in the absence of any individualized suspicion at reasonably located checkpoints...."
What really needs to happen is people need to push their Congressman/Senator to actually fight for control of the actual border. Because the only reason for any kind defense in depth, which is what these checkpoints are, is due to the fact that we don't have the stones as a country or as either political party, to actually practice controlling our border at the border. The internal checkpoints then become a legally accepted workaround that LE comes up with to try and get their mission accomplished, because our own idiots in D.C. won't do their own jobs, not to mention not letting BP do theirs.
That's where people need to focus their efforts......making change from the top of the funnel down, so to speak with government, rather than fighting from the bottom of the funnel up.
With regards to the general checkpoints themselves and separate from the actual questioning issue above, as an unrelated benefit the checkpoints do at least offer a law enforcement presence in areas where there generally isn't one, or where response times from state/county/local agencies to calls would be extended due to their own limited resources or distant locations. USBP agents routinely respond to motor vehicle accidents, do motorist assists, and also respond to state crime felonies such as domestic violence / robbery/ home invasion/ shootings/ murders etc at the request of local agencies to handle the scene until the local agency can take over.
This particular one was just down the road, a few miles north of the I-19 checkpoint, where the fire department response was about 15 minutes: https://tucson.com/news/blogs/police-beat/border-patrol-agents-rescue-man-from-burning-car/article_1d0f279a-f82f-11e3-9277-0019bb2963f4.html
This one was the month prior, 1.5 miles south of the Sarita, TX highway checkpoint on Hwy 77: https://www.kveo.com/news/border-patrol-agents-rescue-man-burning-truck
This one in California, in the El Centro sector: https://www.ivpressonline.com/quicknews/two-men-agent-help-unconscious-woman-from-submerged-vehicle/article_3c704e6e-d4b4-11e3-aa80-001a4bcf6878.html