I don't believe you're powerful enough to cover an entire nation with water.
I make a water shield separating the Fire Nation from the Air Nation

Yeah, but there are only 150 people in your nation.
Also, if you could put a water shield over an entire nation, you could just as easily make a tsunami hit their entire nation.
I'm WaTeR NaTiOn aNd I'm nEuTrAl, bUt I cAn'T sTaNd wAr.
#CeAsEfIrE
I kNoW SeCrEtKeA, tHiS iS yOuR tYpInG sTyLe, bUt I fElT lIkE iT.