To be fair both the US and EU are a federation of states (the latter sharing aspects of a confederation as well 1. In the US all state borders do look like this, so in a way free travel among the ‘independent’ states is allowed the same as in the posters picture.
Why can’t we have this with Canada and Mexico?
Because America is in-between
/s
Actually if you leave Quebec towards Vermont, the pavement changes significantly and becomes pink-ish.
To be fair both the US and EU are a federation of states (the latter sharing aspects of a confederation as well 1. In the US all state borders do look like this, so in a way free travel among the ‘independent’ states is allowed the same as in the posters picture.