Seems like south america is much more hassle than driving in europe.
As long as you stay entirely within the Schengen Treaty area there are no hassles changing countries because there are effectively no borders and no border posts (although there can still be quarantine posts).
Travelling into other areas does involve formalities. Into the UK from the continent is easy like going from US into Canada. Into Morocco about the same as into Mexico. Eastern European countries also pretty easy with visas available at the border.
My limited experience makes me think that a lot of border hassles are self inflicted and you only have to read the occasional post on border crossings on forums like this to see that there has got to be a reason why some people have endless problems and the majority have smooth experiences.
Come September, I will have personal experience to back up all I have read about border crossings in southern S America because we will probably cross borders about 20 times during the 6 months.
One good thing is that there are a lot of long-term travellers roaming around S America and some of them are seriously anal about keeping records and publishing every little detail of every border crossing so you can roll up to the border and know what colour door to open to do the paperwork.