[josephg]

Are they hard to get? I’d expect transferring through the US to be significantly easier than travelling into the US for a conference.

[klausa]

They require issuance of paper visas and an in-person interview. It's _easier_ than B1/B2 visas; but in the overall scheme of things not _that_ much easier.

[mikepurvis]

For a person deliberately avoiding the US (whether out of principle or otherwise), I can't imagine a trip through customs for a transfer would be acceptable either.