What land border checkpoints for outbound? Are they going to double the staff for CBP, which is what all of this requires. Are they going to build a new facility at every land crossing, since there's nothing on the outbound side now in most cases? What about car lanes, are they going to build outbound checkpoints for each lane on each road?

For boats, are they somehow going to put a CBP station at every small inlet along the who-knows-how-many thousands of miles of coastline? How would they enforce that?

Someone in Congress may be screaming about "outbound immigration" but from a practical perspective, it's not remotely doable without spending hundreds of billions of dollars. SusanYRV had it right with her satire, that's what you would have. And it would still be unenforceable. Look at the current land border crossings where, theoretically, you now need a passport or equivalent to return without a secondary. Thousands are still crossing every day on a drivers license with no ill effects. DHS can scream all it wants about what it feels are requirements but in the end, they can't stop people from leaving and they certainly can't prevent a citizen from re-entering even if they have no ID of any sort. You may hit a secondary for a short while as they confirm your citizenship but in the end, you'll have no real problems coming and going.