The Supreme Court has held that the Constitution only applies to U.S. territory.
Yeah, and they fucked up Korematsu, Dred Scott and Kelo too. What's your point?
Technically it is Cuban territory being leased to the U.S.
Which is irrelevant to the bill of rights. The fifth amendment doesn't say "unless you stash the people you kidnapped on foreign soil". For any American official to hold anyone in custody without trial is a crime.
all countries need to protect themselves from unlawful entry
This is a reason for positively identifying anyone seeking entry. It's not an argument for violating their 4th amendment rights.