Thanks to this Reddit discussion, we have a consolidated list approved by Americans on what you can't do when you tour the US
1. Don't underestimate the travel time between cities and states because it is a large country
2. If you go to Florida, do not swim on lakes, ditches, channels, or questionable bodies of water
3. Be careful because laws vary from state to state
4. Follow the instuctions of the police officer if they pull you over
5. Taxes are included upon checkout so budget accordingly
6. Do not pet trash pandas at all cost
7. The photo is not free and if you don't pay up you better get ready for a screaming match
8. Do not underestimate the dangers of American wilderness
9. Be prepared for all things when you plan to hike and do not go alone
10. Not all American cities and towns are walkable. The main mode of transportation is still private vehicles.
Also, most Americans will talk to you like you have been friends for a long time
11. Do not entertain people at the checkout encouraging you to sign up for a credit card
12. Do not make eye contact at New York City subways or get on an empty subway car
13. National Parks are highly protected places. As they say, "take nothing but photos, leave nothing but footprints."
14. Do not underestimate the heat in the Southwest
15. Do not haggle at stores and restaurants. If the staff decline, do not yell at them because it's not their fault.
16. Do not use this particular "C" word
17. Respect the integrity of the line
18. The minimum legal drinking and smoking age is 21 not 18 years old
19. Tip your waiters and service staff
20. Listen to what the locals have to say when it comes to good and bad neighborhoods in their area
21. Do not even think about bribing or sweet-talking police officers
22. American healthcare is messed up and if you can, purchase traveler's health insurance for the entirety of your visit
23. Here are some topics of conversation to avoid:
24. Do not be racist
25. It's the American way of saying hi. You can reply, "Good! How about you?" then go about your day
26. Do as the guides say
27. Respect your host country's traditions and celebrations
28. Do not maintain eye contact for a prolonged period of time because you will get in a world of trouble. Plus, respect people's space.
29. This will freak visitors out but some Americans have a permit to carry their firearms unconcealed.
30. Do not walk on grass that is above ankle-height unless you want viruses and diseases from little critters or a surprise encounter with a snake
The United States of America is a beautifully diverse country. America has a lot to offer if you visit with an open mind, a lot of time, and a considerable amount of money.
You will surely meet a lot of good people who will point you to the best places in their locale. Be mindful that you are a visitor to their home and you'll be alright.