Don't remember the size of Japanese tomatoes. I suspect they are probably similarly sized otherwise I'd have some sort of feeling about them.

I only saw zucchini for sale once in Japan and, for what is nearly a prolific weed -- can hardly give away all zucchinis if you have one plant, the zucchini cost like $10 a piece so I refused to buy them.

The most commonly sold variety of eggplant in Japan is the Italian type which is hardly sold in the US and naturally smaller than the US standard regular / classic type. So not really comparable.

Cucumber variety is also different. The US normally sells straight 8 type. The Japan variety is, I think, a Japanese cucumber and a different type. So not comparable.