How would one go about maximising the participants, length and death-toll of WW1? In particular are major American and East Asian theatres plausible?
A few ideas I have include delaying America's entry into the war, giving the Central Powers time to strengthen their position and last longer, having a US intervention in Mexico in 1918, which Woodrow Wilson originally wanted to do, result in several Latin American countries declaring war on the US in response, adding a whole new theatre to the war and giving German U-boats bases in the Caribbean and Pacific, and a large scale uprising in India.