Is there evidence for continent/ocean placement affecting convection currents in the mantle (and thus plate movements)? Is there evidence for any changes in co

Is there evidence for continent/ocean placement affecting convection currents in the mantle (and thus plate movements)? Is there evidence for any changes in convection currents? i.e. what do we have to go on, besides back-extrapolation of observed drift (happening today, and in "recent" geologic past, e.g. reversal of magnetized direction)? Why should the continents recombine into a supercontinent, rather that drift arbitrarily? Is the idea that, sooner or later, a traffic jam will occur, where first two bang into each other and can't move, creating a larger obstacle, which another then collides with... but since there's some process for a supercontinent to separate, what's the neccessity for this process to not tear apart the collided continents before a full supercontinent is formed?