1. US wants Gaza gas in the Mediterranean.
Gaza has no exclusive economic zone, or even territorial waters. Israel never transferred any control over anything beyond the water line, and did not even fully transfer the land. This was an important point of all the negotiations. So all the natural gas off the coast of Gaza belongs to Israel. If the US wants it, we would have to go to war with Israel.
2. US wants all that shipping money going from east to west.
Gaza does not stretch to the Indian Ocean. That means a canal from Gaza would have to either go through Egypt or Israel. Egypt would defeat the whole point, because Suez Canal is already in Egypt. Therefore it would have to go through Israel. Going through Israel means over Mount Ramon. It would not have to go over the peak, but the mountain is basically over the entire area to the border with Egypt.
The Panama Canal is a modern wonder for raising ships 85 feet above sea level with lots of water. A Gaza Canal would need to raise ships over a thousand feet above sea level with absolutely no water. Rather than sand, like in Suez, it would have to go through very solid rock. It would be two to three times the size of the Suez Canal, but that seems like a minor problem compared.
And what would we get for doing this impossible feat? Egypt makes a little less than $10 billion a year off the Suez Canal, it has never made more. We would not be able to make that much, because we would be competing with the Suez Canal(which already has the cost of initial construction paid for), and just going around Africa(which is not prohibitively expensive). We would not make half as much, so lets say $3 billion after the price war was done.
$9.4 billion in hard currency is a lot to Egypt. $3 billion is nothing to the USA. This would drive a major problem with Egypt.
And remember we could deny enemies nothing. Egypt would gladly take any ship we denied, or they could just go around Africa.
3. Israel wants all the land owned by Palestinians.
The reason Gaza exists is that it is so little land with so many Palestinians on it. It is literally the most Palestinians with the least amount of land. I do not think we will stuff them on less land.