Many Americans have committed no evil at all and are just regular people trying to enjoy their lives the best they can with their given circumstances.
This is the case with most of the societies. But the societies are not ruled by these people. People who make the decisions are the one ruling the society and they are the one responsible for all the actions, but
the regular poeple who just want to enjoy their lives also share some responsibility for not stopping those who are incharge. Afterall the ones who rule are elected by these regular people.
Well, in the case of the United States and also other western democracies, you must realize that those people who are mostly innocent of the policies of those countries are trapped in some kind of political/power monopoly which do not allow them to get better leaders who would not commit evil and attack other countries for the sake of the pursue of power or territory. The case of the United States is the most obvious and the easier to understand. The people from the USA are trapped between the Democrat and Republican party, those who are disappointed with the Democrats go and vote for Republicans, those who are disappointed with the Republican go and vote for Democrats. If there is a group of people who is considering not to vote or do it for an independent they are called out to vote for one of the two hegemonic parties.
The media is controled by people with strong ties to both Democrats and Republicans, they ignore other parties in purpose so they won't catch voters and make them weaker against their long-standing political rivals.
In that system like that, there is not much the average people can do in order to change the quality of the president, the representatives or the members of the Senate. Any alternative beyond voting would be considered to be an act of rebelition or against the State.