That I was nearly mowed down by a pickup truck the size of a tank in Pho Cao Noodle House’s parking lot in Van Buren is a testament to how mainstream Vietnamese food has become in the part of Arkansas where the River Valley meets Oklahoma. Once safely inside, I sat next to a group of men on their lunch break discussing Bible verses over plates of fried rice. Another couple debated what size pho to order. The sound of a spatula hitting a steaming…