Speak in another language other than English in public spaces. Lots of people find it incredibly rude or suspicious. I don't personally but I've encountered plenty of people who do. This is particularly true if the state you're visiting was part of the confederacy.

Most Americans are ignorant of languages outside of English. We are a very monolingual country with one of the only exceptions being people who moved here from other countries. But if the citizen your speaking to was born in the United States they most likely only speak English.

This is commonly, and unfortunately, true for children of immigrants. Several friends of mine whose parents moved here from another country refused to teach their child their native language so that they would blend in better in the USA.