Both the Nazis and Soviets were driving for total victory.
The UK could not have remained independent - either the Soviets would have defeated the Nazis and conquered Britain, or the Nazis would have defeated the Soviets and conquered Britain.
Whoever won would then have moved to consolidate the British Empire and have seized Canada, India and Africa and entered into an alliance with China.
The US would have wound up completely isolated, with no export markets and with its northern border a staging ground for invasion.
Hoover was a completely useless sack of dung for many reasons, but this kind of analysis underlines it.
Actually, Hoover was a great engineer and a selfless humanitarian. He just wasn’t a student of the free market. He was an implacable anti-communist and did have sources of information we don’t, at home and abroad.
Whoever won would have been much weakened. The reason Hitler started WW2 was that his system was a complete bust economically -- he HAD to conquer and loot other countries to keep afloat. Stalin was in much the same boat. We would have been better off supplying Britain while Germany was occupied elsewhere.