Doesn't stop further action based on your private data and retribution for evidence of anti-American speech or potentially-criminal travel patterns. In terms of government surveillance, evidence doesn't need to be submitted to court. It can be provided to a government surveillance contractor like Palantir or Flock for national security purposes.
The current Exectutive Branch has a history of keyword-search driven action, without a chain-of-command of proper review before action.
At least one American citizen has successfully been un-deported based on bad information resulting in deportation action. DHS has a Predictive Policing division willing to conduct unconstitutional, warantless parellel construction.
Warrantless surveillance is well established, and anti-American evidence may exist on your device depending on the reasonable suspicion provided by other Palantir-esque analysis of your online activity and your level of support of the ruling power. The law enforcement agent you encounter won't receive that context, just that the system they usually use flagged you as suspicious without your knowledge (depending on the jurisdiction you're in).
To your point, it only needs to be justified in court if you take legal action. Per Egbert v. Boule (2022), no remedy for American citizens seeking damages for unjustified violations of the First Amendment or Fourth Amendment when it comes to immigration enforcement-related action exists unless explicitly defined by Congress (which it has not, yet).
Edit:
> “People in the government violated my privacy by reading my private information”, on its own, is not a harm the court can fix.
Basically, the average American should treat Border Patrol agents like they're the Gestapo going after their private, Constitutionally protected information with no legal recourse for that potential violation of Constitutionally-protected right to privacy.
If you're rich you can fight it, but the SCOTUS will likely determine Border Agent overreach is something that just happens until Congress establishes a penalty.