Hey, on Fanfiction.net, there are these two stories, America vs Riders and When Worlds Collide. They are both good stories in their own rights, and I suggest you check them out.
America vs Riders: http://www.fanfiction.net/s/9382132/1/America-vs-Riders
When Worlds Collide: http://www.fanfiction.net/s/9276305/1/When-Worlds-Collide
I hope you guys like these stories as much as I do.