If I own land(in the U.S.), can I create a private helicopter landing spot for my personal use? Would I have to register with the FAA or some other government agency?
Helipads have the same issue as runways (as mentioned in the comment above: If I own land, can I create a private runway on my property for my own use? )
Generally, local regulations (State, County, City) are what can make it difficult. As part of planning to create a huge Amazon complex in NYC, Bezos wanted to be able to land his helicopter there. With enough $Billions at stake, he was able to get approval:
Although, that deal ultimately did not go ahead.
The other thing that can be an issue is insurance for a helicopter that might not allow off-field landings.
It would be much easier for example, if it were on your own farm, when you use a helicopter to spray crops.
Essentially, the FAA doesn't care, as long as it doesn't interfere with other airspace. But, local regulations might.