The international box office for the Marvel Studios movies is largely a result of effective brand building and consistent quality. Or, at least, there would need to be some kind of extremely substantive counter-argument, because the raw numbers support the former idea. International box office for those movies:
Phase 1
IM 266, TIH 134, FA 176, Thor 181, IM2 312
Avengers 895
Phase 2, first part
IM3 805, TDW 438, WS 454, GotG 440
Age of Ultron 946
Phase 2, second part AM 339, CW 745, DS 445, GotG2 475, HC 545, Ragnarok 532 (this will end a bit higher)
We should keep in mind that the dollar got stronger soon after the first Guardians movie (between Guardians and Age of Ultron), so the numbers in the second part of phase 2 are somewhat deflated. In terms of actual business being done overseas, the trend is even more obvious than the numbers make it appear.
So that is the brilliance of the Marvel extended universe experiment. The individual properties benefit from the overall success of the venture, with a big spike for the event movies, particularly Avengers.
Ant Man is the lowest of the recent movies, but still higher than any phase 1 movie, in spite of a stronger dollar deflating the number. It's somewhat closer to movies like TDW, WS and GotG than the number makes it appear.