EU citizen here. Not a lawyer so correct me if I'm wrong. :)
WhatsApp uses "privacy shield"[0] to allow it to flow data from the EU to the US.
However, privacy shield was rejected by the European Court of Justice on 16 July 2020 (Schrems II) [1] so we're back to "standard contractual clauses" [2].
There's currently no alternative to Privacy Shield.