The Caravelle was not always a direct competitor. Around 1960 there was a considerable effort by Sud to come to a joint manufacturing deal with Douglas of the Caravelle in the USA, they even had a plant identified, the old Douglas prop aircraft facility in Santa Monica they had vacated when DC8 production went to Long Beach, and at least one Caravelle demonstrator was painted up with Douglas titles and toured the US airlines. There was a bad taste left in Sud's mouth when, after all this expenditure and technology transfer, Douglas said "thanks, now we'll do our own".
The reason behind the Boeing/Douglas dominance can be seen in the actual orders placed and jets delivered in the 1960s; more than 50% of the total world jet market at that time was sold in the USA. European airlines ordered 3 or 5 707s at a time, US carriers like American or TWA took 30 or 50 in the same time. A bit of this market was taken by the European manufacturers but mostly it went to the home companies. For example, the only sale the Caravelle made in the USA, to United Airlines, which was done with Douglas's backing, was only concluded when Douglas agreed to take an equal number of United DC7s in part exchange.