Before America was 美國, it was the flower-flag country. Chinese merchants at Canton in the late eighteenth century met a new ship with an unfamiliar ensign — stars, stripes, a great deal going on — and named the country after the cloth.
What makes this more than a curiosity is that the name never actually died. It went underground into two products and stayed there.
花旗參 is American ginseng — still sold under that name in every herbal shop in Hong Kong, still meaning ginseng from the flower-flag country. The root arrived through the same Canton trade that named the flag, and the name stuck to the commodity after it came unstuck from the nation.
花旗銀行 is Citibank. Not a translation of “Citi” — a survival. The bank arrived in China while the old name was still current, took it, and has kept it through every rebranding since. Its Chinese name means the flower-flag bank, which is to say the American bank, which is to say what everybody called it in 1902.
So there are two names for the United States in daily Cantonese use, one of them a fossil, and almost nobody notices because the fossil has a job. You can walk into a pharmacy, buy the flower-flag root, and pay for it at the flower-flag bank.
The replacement, 美國, is a different kind of name entirely — a fragment of a sound, not a description of a thing. That story is in the flattery canon.