Regarding Franklin Roosevelt and WW2: Roosevelt did not make operational decisions for his military. He left that up to the theater commanders who in the case of the European Air War were Gens. Eisenhower and Arnold. The same criticism of Roosevelt could be made against Churchill; British bombers had just as long a range as US bombers for most of the war. And Churchill himself ordered the bombing of Dresden, which had no military significance.
I consider both Roosevelt and Churchill to be heroes. They saw the evil of fascism before anyone else did. And they worked together — illegally, before the war — to put it out of business. And B”H they succeeded. Yes, the railroads should have been bombed. But think of what would have happened had Lord Halifax become PM in 1940 — or had Robert Taft been elected President the same year. Halifax was an appeaser worse than Chamberlain and had more support within the Conservative Party, but fortunately he yielded to Churchill. Taft was a die hard isolationist and fortunately they masses of the Republican Party masses outvoted their party leaders and nominated the outspoken internationalist Wendell Willkie so US foreign policy was not an issue in the 1940 election.