Right, another one of the those traditional 'construct a more-or-less plausible timeline' exercises.
Your mission, should you choose to accept it, is a biggie. You must devise a timeflow, with a starting point no earlier than 1878, in such a fashion that a state encompassing the Kingdom of Romania (1920-1939) and a western frontier on the river Tisza survives until the present day (and keeps on survivin').
You're allowed one territorial 'off', the "Cadrilater" region (Southwestern Dobrudja).
The resulting state doesn't necessarily have to be a kingdom; it may be a presidential, demipresidential or parliamentarian republic.
You may employ as many plausible nodal shifts as you see fit. Bear in mind, however, that accumulating several large shifts (like, say, both Hitler dying in the trenches and Lenin getting shot by an overzealous policeman) may destabilise the flow enough that subsequent events may not be discerned with any amount of plausibility. Also, do try to refrain from psychosocial ones (again, for example "What if Carol II doesn't become a hedonistic playboy").
Good luck.