The US has fought an ungodly number of wars in its 250 or so years of history, starting with the American Revolution itself -- more than 150, most of which you and I have never heard of. Mostly, these have been commercial wars, the familiar struggles for wealth and power, layered with whatever ideological or mythological justification was then in vogue: fighting communism, defeating terrorism, or occasionally even defending US sovereignty in the form of two US Navy sailors seized from a small dinghy off the coast of Veracruz. Did you know the US invaded Mexico in 1914? I didn't. US oil interests in the Veracruz-Tampico area were endangered during the Civil War in Mexico triggered by a military coup there, and the Navy and Marines charged right in with guns blazing, sparked by the infamous affair of the US-flagged dinghy.
Gangsters of Capitalism is nominally about the decades-long career of US general Smedley Butler, who seemingly fought in every one of his country's wars from the Spanish-American War in 1898 to his last skirmish sometime in the 1930's. The incredible litany of wars, large and small, in which he fought is either eye-opening or mind-numbing, depending on your tastes. These include: Cuba, the Philippines (more than once), Haiti, the Dominican Republic, Panama, the Canal Zone, Honduras, Mexico, China, and I'm sure others I've forgotten. Butler's career provides the narrative thread to unify this tale of old-fashioned US imperialism, complete with colonies and their trappings, though we were careful to never call them colonies.
The author traveled to all of the places where Butler served and fought, using these travels as a means of also telling the contemporary story of these countries, showing the impact of the US interventions of a century ago. It's not hard to see the roots of the instability of those shaky democracies in Central America, for example, undermined by Spanish colonialism and endless US military interventions, backing the interests of US agricultural firms and of local economic and political elites who promised to support US interests. There's a reason these countries were called "banana republics": their governments stood or fell at the pleasure of the United Fruit Company, of Chiquita banana fame.
And Smedley Butler, the US Marines and the US Navy were always there as the sharp point of the spear of US policy.
Eventually, even Butler, raised as a member of the Philadelphia elite and son of a powerful US congressman who helped speed his son's rise through the ranks, figured out that this was all a game in which he and his comrades were expendable pawns. Nearing retirement, he shed his apolitical stance, published a book called "War is a Racket", started speaking out in front of groups of angry veterans and other like-minded folks, and was soon out of the military.
All of this might be of only historical interest if the US as a country had learned any lessons from this sorry imperial past. Arguably, it has made some progress, though the pace of US warmaking has not slowed down much if at all. Sometimes the wars even make moral and strategic sense: Bosnia, the first Persian Gulf War and (in the form of massive aid only, so far) Ukraine. But then there are nutty ventures like Iraq, a thinly veiled intervention in support of oil interests, fueled by deep historical ignorance, misplaced ideological delusions about fighting terrorism, a dash of racism, and a weak George Bush Jr wanting to look stronger than George Bush Sr.
The US still struggles with the duties and responsibilities of being a superpower, at least as much as in Smedley Butler's day.