"Investigation" is a pretty generous way to label "some thugs working for an authoritarian state want to look for incriminating stuff - including criticism or mockery of them or their leader - on your communications device".
Whatever the American legal system may say, a couple of thugs with no warrant conducting searches and seizures of data is a blatant violation of the Constitution's intent. This is the sort of behavior Americans used to rightfully condemn.
The Border Patrol have been a violent and abusive branch of government since their inception. Their abuses under Republican and Democratic Presidents alike have been reported across the spectrum of America's media for many years. 'Thug' with it's roots in groups of violent organized criminals who preyed on travelers - is an accurate description for them.
I would also like the fourth amendment to apply at the border.
Have you read United States v. Flores-Montano? The border search exception (which I disagree with) is pretty old. Can you find an era in which Americans in general found it objectionable or were united in rejecting its application to data?
Whatever the American legal system may say, a couple of thugs with no warrant conducting searches and seizures of data is a blatant violation of the Constitution's intent. This is the sort of behavior Americans used to rightfully condemn.