Final answer:
It is uncertain whether stronger American policies in the 1930s would have deterred the formation of the Axis powers or influenced their adherence to international law, due to multiplicity of factors such as economic conditions and ideological movements. American isolationism was strongly supported by the public and changing that course of action could have had unpredictable effects.
Step-by-step explanation:
The question of whether stronger American policies in the 1930s would have compelled Germany, Italy, and Japan to adhere to international law is a complex historical issue that encompasses aspects of diplomacy, military power, economics, and the politics of the era. The policy of Isolationism adopted by the United States during the 1930s was largely a response to the widespread desire of the American public to avoid entanglement in European conflicts. It is uncertain whether a more proactive American foreign policy would have stopped the formation of the Axis powers, given that there were many other factors at play, including the Treaty of Versailles, economic conditions, and ideological movements that were already pushing these countries together. Furthermore, the U.S. had limited direct influence over these nations' internal politics and their expansionist ambitions.
In the hypothetical scenario where the U.S. decided to engage more robustly in international affairs by, for instance, enforcing economic sanctions, increasing military readiness, or forming strategic alliances, it’s possible that these actions might have influenced the Axis powers' decision-making. However, it's also plausible that such American efforts could have had the opposite effect, provoking a stronger resolve in those nations to pursue their goals. The actual impact of hypothetical stronger U.S. policies is a matter of speculation and debate among historians.