Final answer:
A historian would be able to use this source to support the claim that not all Americans supported joining the war.
Step-by-step explanation:
A historian would be able to use this source to support the claim that not all Americans supported joining the war. The quote provided by Charles Lindbergh suggests that there were people who opposed intervention in the war. Lindbergh mentions a policy that leaves Americans free to follow their own way of life and develop their own civilization, indicating a sentiment of isolationism or non-intervention. This aligns with the claim that not all Americans supported joining the war.
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