Are we a christian nation? I believe we are a free nation. Everyone is entitled to their own opinions as well as religions.
Halloween was formerly known as All Souls Day (and a few other names) and is a CHRISTIAN holiday. People would ring bells for the souls in purgatory and would bake soul cakes and hand them out to poor children in return for them praying for the souls. Which would be trick-or-treating today.
Some believed that the souls would come back, looking for vengence on enemies, which is why people started wearing costumes.
This is not an evil holiday, it's a day to celebrate the dead.
Consumerism has turned it into a fun holiday where kids can be anything they want for one day and get free candy in the process.
Everyone likes to be scared sometimes, just because you put out a few plastic tombstones on your front lawn and hang up a ghost windsock does not mean you are celebrating the devil. It's a great holiday, and is of Christian origin.