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.
When you leave Quebec towards Ontario, the road is significantly less bumpy.
When you leave Ontario for Quebec, the road signs become incomprehensible.
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.