Be assured by a frequent visitor to the States (another holiday coming up), that you are not being mocked - it is a smile of recognition that you are from overseas, and sounding 'British', in using 'proper' instead of 'pronouncing it right'; and 'proper' instead of 'real teacher'. If anything, most Americans will be even more friendly to you, recognizing that you must be a visitor, than in any way mocking or disparaging. You will have to forgive some of them if they betray a smile that suggests 'patronizing': their belief that the USA is the greatest nation on this Earth has worked its way into their genes.
If not, and you are being mocked: 'it takes all types' and you'll find the uncouth, the yoboes, in every country.
What's American Eng. for that? I would be being unfair to 'rednecks' and even 'trailer trash' to impute such bad manners to them.