The next steps in the journey of Sir Fynwy are a little muddled, in that whilst no legislation was ever passed annexing the county into England individuals began to express doubts over the 'nationality' of the county. Thankfully, some clarity would be added in 1746.
The Wales and Berwick Act ensured that any and all cases "where the kingdom of England, or that part of Great Britain called England, hath been or shall be mentioned in any act of Parliament ..... (will) include the Dominion of Wales".
What this act did was ensure that it was clear that any parliamentary or legal reference to England also included Cymru without any doubt. As really, up until that point, the use of the word had been ambiguous.
The next big challenge for the county would occur almost a century later. In 1847, the 'Blue Books' (and I would encourage anyone who hasn't heard of the Blue Books to go look them up) were published. The books, in some respects, would help to create a debate around 'Welshness'.
Commissioned as a report on education in Cymru, the books certainly took a negative viewpoint on the language. Whilst the linguistic borders of Cymru were shifting, as the border regions became more English speaking, there were still hundreds of thousands of Cymraeg speakers.
Many of those speakers lived in Sir Fynwy but by the late nineteenth century those numbers were, of course, decreasing. So if you are to judge 'Welshness' on language alone then this an area where confusion can arise.