They don't need a search warrant for Iceland
How 'bout some critical thinking?
The 4th Amendment is part of the Bill of Rights. The rights enumerated therein are not privilege granted by nature of geography. They are inalienable rights, endowed by the creator. If the right applies to any human within the boundary of the USA, it applies to all humans anywhere.
That is not 100% true. Constitutional rights only apply to US citizens regardless of where in the world they are. The constitution does not grant any rights to anyone who is not a US citizen.