It goes to Congress now. But after that, it’s uncertain. The JCPOA is not a formal treaty. It wasn’t incorporated into U.S. law by an act of Congress, which means it does not require an act of Congress to reverse.

Here’s another line from Trump’s speech (emphasis added)

However, in the event we are not able to reach a solution working with Congress and our allies, then the agreement will be terminated. It is under continuous review, and our participation can be cancelled by me, as President, at any time.