Yes.

Ron Swanson is an exaggeration but it's being used in that manner here. Normally ethnic would refer to something from farther away than our southern neighbor.

as other comments have pointed out it isn’t really always meant maliciously. there’s literally aisles in stores all across the continent labeled as ethnic and people understand what it means. there’s usually a collection of imported foods.

it isn’t just white people being racist, this is a continent of immigrants where there are so many minorities that the old world, traditional ethnographic lines start to blur and fall apart. you hear black and latino people using the term all the time. old vietnamese grannies here in the middle of the country say it a lot. the fact of the matter is there is a white majority undercut by significant black and latin minorities in most demographics across english-speaking north america with a smattering coalition of smaller yet minorities that, when put together, have enough power and political capital to have a seat at the table with everyone else. ethnic is one of the catch all terms that ends up getting used both inside and outside the group, and not just in food. it’s just a part of the north american english dialect continuum.

that said, racists do tend to use the word as a euphemism when they really want to say a slur but can’t.

but anyway, in short: OP is basically correct. it literally does just mean “you’re from somewhere and it isn’t here bc you’re not like one of the 3 kinds of people we usually see.” if you’re not someone who lives on the american continent you might have trouble understanding why people find utility in such a term but it is a functional term and not necessarily prejudiced.

how racist/bigoted/xenophobic the connotation ends up being depends on the person.