They do, but only because it's been adopted from British media and literature. You might even say it's a symptom of being over-read, if that's possible.
"An historic" is certainly used in the US, but it's wrong in all contexts.
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The British pronounce it as "istory," so they use "an" before.
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"A his-toric day"
"An his-toric day"
Both seem to work correctly with American pronunciation.
Journalists and films seem to use "an historic" with an American accent, which breaks the rule but still feels correct.
For most words the indefinite article is clear. This one feels weird.
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"An historic" is certainly used in the US, but it's wrong in all contexts.