Without colonel Parker born as Dries van Kuijk in Breda, North Brabant, the Netherlands, Elvis could have become a even bigger star outside the US. Colonel Parker didn't want nor arrange performances or even a tour outside the US (with the exception of Canada); some speculate that this may have something to do with the fact, that colonel Parker (Van Kuijk) was afraid that he was considered an illegal alien in the US or even a stateless citizen, because by joining the US army he also had lost his Dutch citizenship.
IMHO more internal performances/tours would greatly benefit the popularity of Elvis outside the US.
I have a hard time picturing how he could become even bigger overseas? Isn't elvis right now actually more popular overseas than in the states. Doesn't he have like a billion albums sold world wide?
I think this thread is confusing quality for popularity. I think otl is pretty much the largest impact elvis could have ever achieved. He's arguably the most impactful popular entertainer ever (solo artist perhaps if we throw in the beatles debate).