The US was still very much involved in its development and testing, so I think we can still chalk it up as a win for multi-country collaboration, eh :3
> The US was still very much involved in its development and testing
... Wait, how was that? The Concorde was essentially the Franco-British entry in what was once a rather fierce international race to build a supersonic passenger jet (then seen as the future); the US entries were the (failed) Lockheed L-2000 and Boeing 2707.
If the US had been open to collaboration, it is likely that the UK would’ve gone in with them, and we might live in an alternate universe where there was a UK/US Concorde-ish thing, and maybe a French mini-Concorde (the French design which got subsumed into Concorde was particularly small, only 70 passengers). In our universe, though, US manufacturers were sceptical of working with BAC because they believed that govt funding for a foreign design would be hard to come by.