The Academy of Country Music announced its first round of performers for the 55th ACM Awards: Jimmie Allen, Kelsea Ballerini, Gabby Barrett, Luke Combs, Miranda Lambert, Tim McGraw, Maren Morris, Old Dominion, Riley Green, Tenille Townes, and Thomas Rhett featuring Jon Pardi. The ACM Awards will air live from Nashville on Sept. 16 at 8…