What is "uniquely American" about the word apple? Both the word and fruit come from elsewhere and still abound in those places: the word came into use in English over a thousand years ago, and the first apple tree to grow in the Americas would have been planted by a European settler some centuries later. There are cultural associations with apples in America, but do these attend to the word or the culture? And are they necessary for an understanding of the word 'apple' - whether by someone learning English as a second language, or as their first but in another part of the world?

Perhaps you mean that 'apple' has a different meaning in the United States than, say, in Wales, because its web of implications looks different in one place than another. Following that thought, though, the same would be true of two American speakers, who surely have their own idiosyncratic webs. It's an interesting idea. But are words not 'synonyms' that have the same referent, only because two speakers have different relationships to that referent? Is a word partly its evocation? Or can we look at its evocation separately from a stricter 'meaning' it shares between speakers? (Surely it shares something, or language would lose its point.)

Incidentally, synonym is not the word to be nullifying here. A synonym is a like word, something that may equal the original but usually differs in degree, amount, tone, allusion, or other effect. Anyone using a thesaurus without a dictionary is sure to embarrass themselves sooner or later: differences in meaning between like words are common, and it is no revelation to say that one speaker will have different associations with a word than another, particularly if they come from different cultures.