I would say it is fairly common among people who have not been well educated, and who don't read very much. But most native speakers of English know that he/she/it use "doesn't" and everything else uses "don't."

Not just in the USA! It's a running joke - and often true - that bigoted people are incapable of basic spelling and grammar skills. I just checked Juror 10's other lines... he's a pretty sloppy speaker. The extra joke is that Juror 11 (who makes the correction) is not a native English speaker - he's a refugee from Europe, recently emigrated, and has a thick foreign accent.