It wasn't Churchill
The US never did 'come in on the side of the allies'. It was attacked by Japan and Hitler then declared war on the US. If these two almost simultaneous events had not taken place it is doubtful if US public opinion would ever have tolerated the US entering the war.
I could not have voted for FDR because of his naive belief that Stalin was his friend and his willingness to talk to Stalin behind Churchill's back.
US foreign policy under FDR was trending towards the US joining the war on the Allied side. We sold everything the Allies ordered or requested, we extended them credit & loans when they spent all their money & specie. US Navy escorted freighters halfway across the Atlantic towards UK. We supplied war materiel, food, finished goods & on & on. In preparing for the war, we planned out agencies to coordinate production, prepared to ration food, strategic materials, prepared to establish a military draft, prepared to construct military training camps, airfields, expand ports, run critical industrial production 24/7, upped the defense budget repeatedly, prepped to float war bond issues, & on & on.
With US Navy escorting freighters in the N. Atlantic, it was only a matter of time before a U-boat attacked a US Navy ship - & our ships had orders to defend themselves. We would have shortly found ourselves in the shooting war in any event.
FDR was anything but naïve - look @ his record on his handling of important public issues. Of course he knew that Stalin wasn't his friend. The FBI saw bogeymen under every bed, but in the case of the USSR, they were right. If hopelessly overmatched in terms of tradecraft & the sheer number of agents & spies & the reasons why they acted for the Soviets - & so the FBI (& Army & Navy & Marine intelligence, the State Dept. Intel) were all blind to many of the penetrations. The Soviets ran serious intel efforts against everybody in the West with military or economic or diplomatic force (& especially the US, as we'd been important in WWI & looked to be important again in WWII).
A glance @ West/Soviet history should have told the FBI & the alphabet soup of US intel agencies everything they needed to know: The Communist Party nor Stalin ever forgot that the West invaded Russia, & intervened militarily against the Soviets & in favor of the White Russians. & Stalin never forgave. Soviet efforts in the US dated back to @ least the 1920s.
As for Churchill - he & the Brit military were forever trying to buffalo US forces & FDR. Churchill was trying to avoid massive Brit casualties, as in WWI - & @ the same time preserve the Brit Empire as much as possible. The two goals were contradictory. & so Churchill dithered, & pissed & moaned about the cross-Channel invasion, even though he had committed UK to the effort. Instead, he & Brit military wanted to nibble @ the periphery of Europe, hare off to the Balkans & advance northwards, cutting off the Soviet military &
saving Europe from the Communists. As if UK & Commonwealth could man & equip, transport & sustain, produce the armaments & ammo, tanks, planes, ships, railways & trains. The whole notion was ludicrous - it would have been a fool's mission to even try to get between the Nazi forces & their allies on the one hand, & the Soviet forces & their allies on the other. It wasn't going to happen.
Churchill eventually became obstructionist, & kept undercutting Eisenhower in the ETO, & trying to install Montgomery or Brit High Command in charge of ETO, even when everyone could see that the US effort (1942 on) was massively greater than UK's contribution. We needed Stalin to invade Japan, as he'd agreed. Up until we nuked Japan, we assumed we'd have to invade or blockade Japan & starve them into submission. As Britain began to groan under the weight of US troops & equipment & materiel & depots, Chruchill became desperate to have the Brit Navy do
something in the PTO - else the US forces (& Anzac) could argue that they'd done all the heavy lifting there - which was mostly the truth.
