The prices would surge high and thee quantity available would go down massively.
Explanation:
Malaya was very strategically important as a primary source for rubber for US automobile industry, which was one of the biggest in the world.
When Malaya fell to Japan they would obviously cut off the rubber supply to US that went freely under the British. This would mean that US would be without a primary source for their manufacture.
Thus the prices would surge high and the automobile industry will take a massive hit.