Look up the Treaty of Ghent, 1814. That's pretty much the formal international recognition that the US was capable of defending itself against all comers. The Duke of Wellington, at the time, when asked about America, give this observation:
I think you have no right, from the state of war, to demand any concession of territory from America... You have not been able to carry it into the enemy's territory, notwithstanding your military success, and now undoubted military superiority, and have not even cleared your own territory on the point of attack. You cannot on any principle of equality in negotiation claim a cession of territory except in exchange for other advantages which you have in your power... Then if this reasoning be true, why stipulate for the uti possidetis? You can get no territory: indeed, the state of your military operations, however creditable, does not entitle you to demand any.