Mark Twain was not sympathetic towards the US attitude to the Philippines. He was an Anti-Imperialism and joined the Anti-Imperialist League.
He published his opinions on Imperialism on many newspapers, on October 15th of 1900 he expressed that he left America - during this time he was lecturing in Europe - an imperialist. But he noticed that the US did not plan to give the Philippines independence so soon, instead, the US wanted to subjugate the people, using torture techniques and engaging in massacres of insurgents that fought for independence.