International Travel- US re-entry requirements

This has nothing to do with Covid testing, but a funny story about re-entry into the US after traveling overseas. I went to Italy for a summer, went hiking in the Alps and just kind of touring about. At some point, I had my passport in my back pocket during a rain storm. Everything I had with me was soaking wet. I didn't think much about it and just kind of set my passport out to dry for the night and carried on with my trip. However, upon entry back in Atlanta, I was flagged and moved to another section because they suspected my passport was fake. It seems that the water caused the blue cover to bleed through and form these blue spots all over the image/details page. This was years and years ago, but from what I remember of the conversation, they informed me that the passport was designed for this not to happen and thus I, or someone, had tampered with it. Even though I had a Louisiana drivers license, a college ID and several other forms of ID, I still ended up sitting in customs for several hours waiting until they finally showed back up with a faxed copy of my information to prove I was who I said I was. Thankfully, I didn't end up missing my next flight since I had quite a lengthy wait, but either way it was kind of scary thinking somehow I wouldn't be allowed back into the US. I ended up having to surrender that passport and getting another made, which cost me however many $ that was back then.

Short version, don't get your passport wet.