I love Age of Ultron. I think it's one of the most rewatchable MCU films. However this moment always bugs me on rewatches, especially so since Cap is a WW2 vet and fought in the European theatre.

War, at least in Europe, could have been avoided if only UK and France showed a little more teeth. They also had quite a few chances to do so before it became too late. They could have stopped Germany and ended Hitler's genocidal plans back in 1936 when Hitler ordered soldiers to remilitarise the Rhineland. They didn't do anything when Germany took over Austria or when they didn't honour the Munich Aggrement and invaded Czechoslovakia. They finally declared war after the invasion of Poland and even then they didn't do much for a while while Germany was busy with Poland. They had a pretty good chance of marching towards Berlin unopposed while the German army was busy but they simply didn't take it.

So, yeah, either Cap doesn't know the history of the time period he came from or he is just talking nonsense.
Character moments when you think the character is completely wrong