Chewing gum in the wrong context and in an obnoxious manner can be considered rude just about anywhere, even in the United States. It is considered particularly rude to chew gum in public in countries such as France, Switzerland and Singapore.
Chewing gum was such an issue in Singapore that it was banned as an import in 1992, though this was primarily due to the high maintenance costs of removing improperly discarded gum from public places, including public trains. Chewing gum has the ability to annoy or even disgust people in a variety of different cultures. International travelers may want to either discreetly chew or stick to breath mints.