The proper adjective, or someone from Guatemala, is Guatemalan.
It's an offensive term used against any Mexican, Guatemalen, Brazilian ETC... that lives in the u.s.A derogatory term for Mexicans or other Latin Americans.
It's important to avoid generalizations about any group of people, including Guatemalans. Attitudes and behaviors can vary widely among individuals due to cultural, social, and economic factors. Some may perceive certain behaviors as unfriendly due to misunderstandings or cultural differences. Building empathy and understanding can foster better relationships and dispel stereotypes.