Depends
It would depend on a lot of things.
How many people? Why do they want it? Where else would/could they go? How valid is their claim to the land? What do they want to do with the land. How much trouble would the land they want be to give? Do they have resonable plans to take possession of the land if we gave it to them?
In the end, if there where enough of them that had a good enough reason for feeling the land was their land, I would support them.
However, it isn't a real issue except with the question of Native Americans. They are the only group with sufficent numbers / reasons to lay claim to taking part of the US as their own country.
The problme with American Indians is that they are too scattered and internally divided to make a serious claim. Each tribe wants to retain their own tribal land, which is scattered in small chunks all over the US. If the American Indians could get together and settle on one section of land, I would support handing over some substanial area in the Midwest or one of the costal states and surrounding regions.
Jay