is there any way the England and Scotland could of ever become one Nation or at lest had the same Monarch/Head of State?
Even though Scotland's colonies allow it to far outclass England economically, having the English adopt a Scottish monarchy system isn't very likely: there are just too many English and not enough Scots.
And the reverse is just absurd in recent history: The 18th and 19th centuries were just too bad for England to do anything (What with the loss of Canada and India respectively) to gain a hold over Scotland. Heck, they lost Ireland, Cornwall, and Wales to the Celtic League, so how any POD could change that trend is beyond me.