Risa

Not pumpkin seed flavored, "pumpkin spice" are spices used in American pumpkin pies, namely cinnamon, cloves, and nutmeg. There is no pumpkin in pumpkin spice.

This is from someone who likes pumpkin spice and was also confused about it for a long time.

Like Margot said, it's the spices used for pumpkin pie. There's a relative flavor you see sometimes that's full pumpkin pie flavor, which I prefer. It's more well rounded. Pumpkin spice has, over the last decade probably, fully taken over fall drink flavors. It started with Starbucks lattes, spread to other cafés. Now it's in everything. It has fully taken over the fall beer flavors I think, overtaking Oktoberfest styles.

They rarely eat pumpkin, calling it “squash”, and renaming squash to something else (summer squash or something?)

Admittedly, I and probably 70% of other Americans were formerly unaware that pumpkins are a variety of squash, making this paragraph surprisingly difficult for me to even parse. So that was an interesting and kind of fun experience.

If it helps, I have come to realize after thinking about it that I see any roundish variety, regardless of smoothness or color, as a pumpkin, regardless of its actual name. If it's gourd-shaped (butternut/zucchini), it's a squash.

The flavor is seasonal and therefore novel, you're right about that. But tbf, indian food uses squash in general, which seems to extend to white/orange pumpkins, and we definitely have Indian-Americans. Ditto Hispanic. It is eaten more often than the two holidays, just not by white people.

For the useless naming difference, as always, any beef with America can more factually be blamed on the Europeans. Specifically, the French.