OK.. I no there's a lot of these in here but here it gos.
I don't remember much about this move but I think its one may be tree aliens and some kids and a town running from some people I think. And one of the aliens all ways says he will use a weapon to blow up the earth or something. And I remember one singing that song.(o give me a home where the buffalo roam.. may be! It's a funny movie.
I no this is not much but any help will be vary vary welcome!:)

Spaced Invaders (1990) (http://www.imdb.com/title/tt0100666/)

Your good my friend.. you are the one! just lookd it up and you are right! Sweet!
Every time I would ask someone about that movie they would just look at me like I was crazy.lol thanks

Glad to help.