I don’t really have a dog in this fight, but how does this square up with prices in Europe also dropping?

Because gas is fungible. Since we're burning our reserves, we're importing less than we otherwise would, and from there it's basic supply and demand.

Your own source says you are wrong. The price of a gallon of gas has dropped by almost a dollar according to the article in this post.

Your own link says: “As shown in the table above, our analysis suggests that President Biden’s historic SPR release, in coordination with IEA partners, lowered the price of gasoline by 17 cents to 42 cents per gallon, with an alternate approach suggesting a point estimate of 38 cents per gallon.”

So, even their most generous estimate doesn’t support what you are saying. And that’s assuming that the price of gas wont drop any further (it will).