During WWI, part of the impetus to segregate draftees by region was language barriers. When the 82nd Division was formed with a mix of draftees from TN, NC, and GA, and then received a large group from NY, the language variation was enough to be an operational problem. Since then, increased travel and communications have actually leveled many differences.
Arabic, to use the initial example, has been spread for 1200+ years, mostly during a time of comparatively difficult travel and communication. American English, on the other hand, has been spread out for <400 years, much of that time over a much smaller area than Arabic, with much easier and frequent travel and communications. Getting to Arabic levels of divergence in American English is really, really difficult.