Yes, it is generally considered a violation of U.S. flag etiquette to fly any flag higher than the American flag when displayed together on U.S. soil. According to the U.S. Flag Code (Title 4, United States Code, Chapter 1), the American flag should always be flown in a position of prominence and honor, typically at the highest point when displayed with other flags.
However, the Flag Code is a set of guidelines rather than enforceable laws, and there are no legal penalties for not following it. The code is intended to show respect for the flag, and most instances of non-compliance are seen as matters of personal choice or local custom.
In some cases, local regulations or HOA rules may have their own rules about flag display, but these are separate from federal law.