is it illegal to let an american flag touch the ground or to step on it?

Not Legal Advice: While the federal code contains no penalties for misusing the flag, states have their own flag codes and may impose penalties. The language of the federal code makes clear that the flag is a living symbol.

Parts of United States Code Title 4 Chapter 1 — The Flag say that:

• "No disrespect should be shown to the flag of the United States of America." - Section 8
• "The flag represents a living country and is itself considered a living thing." Section 8j
• "The flag should never touch anything beneath it, such as the ground, the floor, water, or merchandise." - Section 8b

See the full code here.

In 2013, Lil Wayne sparked outrage over stepping on an American flag during the shooting of his 'God Bless Amerika' music video. The rapper pledged that he did not trample the flag on purpose, even though a video clip appeared to show the singer with Old Glory at his feet. - NYDailyNews.com.

Here are 5 ways to show the flag respect, shared by CVSFlags.com