homefree parent
I had a funny experience with a French cheese shop in SF for this - I tipped a $2 bill and he called me back in confused thinking it was fake, but was good natured when I showed him it was real.
Last time I was in Mexico (walked across the border so many Americans in the area and they list prices in both us and mexican currancy) I paid with twos because that is all I had, which really confused the clerk, but her manager had no problem.
I had to go to El Salvador for a work trip a while back and brought a bunch of fresh $2 bills with me. They use USD as the currency there, but they're constrained by what's in circulation. I thought it would be fun to have my $2 bills there for maybe years, I'm not sure if they have any others!