In Europe you don't need countries for this. The smallest federal country will have a clear difference on the road at the border of two federated entities. Worst, it can happen between municipalities in some countries.
I know that place. The borders between the Ellestraat (Hulst, NL) and the Hellestraat (Stekene, BE).
The right side of the street on the Belgian part is actually Dutch for a few 100 meters. If you look around on street view the part with a bicycle lane is Belgian, the part without it is Dutch.
The border-free zone is called the Schengen area. There are still some EU member states that aren't included.
Euronews article
"Austria has blocked the accession of Romania and Bulgaria into Schengen, the passport-free area that has abolished border checks between the vast majority of EU member states."