During the dying days of the Spanish Empire in America by the end of the 19th century, the U.S. government decided to become a replacement empire. Having conquered the American natives. Why not take the Caribbean too? 

So it conducted a 'false flag' operation to fake an attack incident on its navy ship anchored close to Cuba. (Thus began many such false flags in the 20th century.) The ship went down and the invasion of the Spanish Empire was on! It was an easy job. The U.S. took Cuba, Puerto Rico, the Virgin Islands and Philippines. And while at it why not take Hawaii too, which it did. No thoughts were given on the consequences of this grab and plunder so typical of European empires. 

Consequences: Cuba rebelled and became enemy. Puerto Rico utterly bankrupt, 100,000 left the island packed with defeated people. Hawaii is a huge military base and locals do not call themselves Americans. Philippines went independent after attacked by Japan in WW2 as part of the U.S. military empire.