I'm sorry that all happened to you, that sounds really bad. I'm not doubting your experience. However I think it's important for Americans in particular to maintain the distinction between "the Constitution applies and border police are acting illegally" and "the Constitution literally has no force in these situations" when discussing these problems in forums like this one. A lot of the recent creeping fascism involves the fascists treating the law as if it didn't exist, but when actually called on it they back off.

Of course as a practical matter anyone crossing a U.S. border should understand the risk of arbitrary violence, deportation, detention, or having all your stuff taken.