I wonder if the front right lower control arm rear bushing has failed. This bushing is a 'fluid filled' bushing and may introduce excessive play if the fluid has leaked out (not unusual).

I would say it is time for a 4 wheel alignment. If the caster is way off it can cause this. While it is on the rack look for worn suspension parts first.

Here's a new one!   2012 Countryman with 101,000 miles - when steering to the left through a curve at mid range speed (40 MPH +) it feels like the passenger side rear tire is going to fold in under itself - the car almost feels like it is going to jump to the right - there is no vibration or noise and straight travel and right hand curves are fine -  tire wear is normal    any thoughts?!?!