Well, who owns the ship is the important bit. Where the ship is registered is irrelevant because its done for tax etc purposes. The crews are often subcontractor kind of deals. The ports that the ship left/was going to dont matter either, the ship is just a glorified floating lorry, you wouldnt consider a arson attack against a polish lorry to be a attack against germany just because the lorry was going to frankfurt.
If you ask me personally this was an attack against the west, not any individual countries.