I’d wager that most people would assume “largest city” meant “largest city [by population]” because that’s clearly what search results assume. “Largest city in USA” first lists the Wikipedia entry for “List of United States Cities by Population” [0], with the next bunch of results assuming the same thing. For me, the 9th result is the first to mention land area.[1]
Jacksonville, Florida being the largest city has long been a trivia question that relies on this ambiguity. Based on the Wikipedia article, it looks like Anchorage is larger but maybe because it's a county equivalent, it's not considered a city in this context.