I find it strange that you have a default translation. I expect the sort of crowd who would most likely use this will also be very particular about which translation is being served.
¹ “Familiy” because the WEB also has a British/International spelling edition, not present through this API. If anything I think it would make a better default than the American spelling edition. Matches the spelling used by more of the world, and lines up with the KJV better.
Besides, just as a verse is part of a book, so is a book part of a translation. It makes as much sense to declare which bible to query a verse from as it does to declare which book or verses to query for.
But for a site like this, you’re only considering public domain translations. Given that, I think that the WEB is a reasonable default, specifically because of the paucity of available options. And when you have fewer options, I think a default is more useful—“you don’t have the one I want, so what should I use instead?” will cause paralysis that a default resolves.
On the available public domain English BIbles: you’re generally limited to the KJV, a variety of more obscure translations older than the ASV, the ASV, and the WEB. (Fun fact: the old testament of the RSV and the first edition of the new testament are now public domain for most of the world, including Australia where I live. I grew up with the RSV and still use a second edition RSV as my primary Bible.) Out of these, I don’t think there’s much contest: the KJV is popular for historical reasons but a poor default for the aforediscussed reasons; of the obscure translations, most or all are either unconventional in some significant way, or would be widely acknowledged to be superseded by the ASV, by direct or indirect lineage; that leaves the ASV and the WEB which is mostly just a linguistic update of the ASV. That leaves the WEB as a sensible default public domain translation.
When translating orally, it sometimes means a translator has to pause, or guess at how the speaker is going to end sentences/paragraphs. This is because the other language requires an ending element to come earlier
This also has a fun impact on jokes. Sometimes the punch line needs changing, or other jokes become possible -- because the sentence ending gives a different denouement
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Biblical Greek tends to use word order for emphasis, but still with an overall sentence structure very similar to English. So (as far as I know) the issue is mostly hidden for English speakers
For example