Then there is the land that is in the direct possession of the "Crown". The "Crown" is just a technical legal word which means the British State, stemming from times of absolute monarchy when the State and the Monarch were one and the same. But that has been abolished over the centuries and only this vestige remains. An example of land owned by the Crown/State would be Buckingham Palace or the White House.
Lastly there is private land. This is not owned by the Queen nor is it owned by the State. Yes the law provides that the State can take back land into its possession but this right exists in both the US and UK. In the UK it is called compulsory purchase and in the US it is called eminent domain.
The main practical difference is that the US has a constitutional right of privacy whereas the UK does not. The British Parliament is unrestricted in what it can take from you but the Queen cannot simply saunter onto your land and start playing croquet.