There is no international police force that would arrest Biden for violating a treaty. However, a treaty ratified by the Senate is US law. So if we violated a treaty, we're violating the law. And a court would almost certainly shoot it down.

If you want to stop releasing asylum-seekers into the country to await their court dates, then fund more detention centers and change the law to allow the detaining of children. Until that happens, they have to be released. Again...the law. (Well, and resources to build and staff detention centers.)

Yes, it is absolutely true that we would be violating the law if we shutoff most or all migration related to asylum. Even the 5000 encounter limit was legally questionable.

Don't like it? Change the law. Probably won't happen now while you and I are alive, depending on how old you are.