Tbf we win every war we fight.
The matter of occupying territory is where we go wrong. Not really up to the task.
We can occupy territory real good, and occupy a lot of it pretty much indefinitely. But occupying territory isn't actually the goal of a war. Occupying territory just gives the smart people power over that territory so they can enact whatever policies they want. And most of their policies are stupid, which requires eternal occupation lest the conditions that started the war in the first place pop up again.
Fair point on Granada.
I still find it shocking that we continually send troops to distant lands without a declaration of war:
While Congress can initiate war by making a declaration, the President can determine that a state of war exists and react accordingly. ("The President was bound to meet it in the shape it presented itself, without waiting for Congress to baptize it with a name; and no name given to it by him or them could change that fact.") Having interests in a lot of countries, and lots of defense treaties, it's very easy to get drawn into a state of war without initiating a war. And by ratifying the UN Charter, the Senate gave the executive branch, working through the Security Council, a means by which it may make de facto declarations of war in concert with the rest of the UNSC.
Congress, for their part, has recognized a state of war can exist without a declaration from them since at least 1802. It also authorizes specific military operations without baptizing them as formal "wars" (e.g. the 2001 AUMF). Finally, it has given the President carte blanche to fight short wars via the War Powers Resolution, with or without a declaration on either side.
Under current laws, there's no need for a resolution with the magic words, "one, two, three, four, I declare we are at war." It's easy to get into a war, and the President and Congress can stop a war at any time they choose by exercising their commander-in-chief or authorization/appropriation powers.