Not sure how time spent across borders really matters, but I'm foreign born and have spent years outside the US. I'm currently in Chicago and have driven to Florida, New York, Colorado, Nevada and have gone north and south of the border. I frequently visit relatives that live in rural parts of Iowa and Indiana.
My point still stands, you won't find as large a cultural gap as you would traveling to another country.
> Interestingly enough, I referred to places in the US where English is not the dominant language.
Of course you'll find small populations of foreign speaking people in the US, just as you would in any country but you're missing the point. You can't compare going to Chinatown with actually going to China, that's ridiculous.