What offensive weapons can shoot 8500 miles and up’s target?

Like the title

See documentation. Stealth bombers, strategic bombers and conventionel missiles can.

https://www.simcountry.com/cgi-bin/cgip?loadDocument&miDocument=warweapons

If you're new to the War Engine, hitting nations that are closer, (like a neighbor) allows you to use shorter ranged and therefore cheaper equipment and ammo.