How do we know the US lost? Because the US got stuck with Texas. Before the war even started, the US and Mexico decided, “OK, loser has to take Texas.” Because, come on, it’s Texas. Nobody wants Texas in their country. That’s why European nations are in Europe–they want to be as far away from Texas as possible. Lucky Europe!
But now, the United States is stuck with Texas, unless it can find a sucker to start a war with who’s willing to take the bet, “Loser gets Texas.” But sadly, you will not find a nation on Earth willing to take that bet. The US is so screwed.