When Apple unveiled the iPhone 4 on Verizon in February, everyone thought that the iPhone’s cross-carrier distribution in the US would be the end of Android and other competitors. That hasn’t been the case, as Verizon’s adoption of the iPhone hasn’t slowed AT&T sales of Apple’s smartphone at all. Also, overall iPhone market share hasn’t seen that impressive of an increase since Verizon picked up the iPhone 4.

A new report from Asymco details how Verizon is just a “small bang” in iPhone sales, and how the “big bang” is actually happening overseas.

“AT&T iPhone activations show no significant impact from Verizon and Verizon itself shows a modest start to sales[2]. What did not happen is an exodus from AT&T. We also did not see a rejection of the iPhone by Verizon customers long exposed to anti-iPhone Droid advertising. We also did not see a considerable impact of Verizon on growth.”

Verizon has contributed 4.5 million new iPhone users, but the majority of new iPhone adopters are coming from the international markets— Apple’s last earnings call reflected that fact.

The yellow line indicates Verizon iPhone sales, while the green line shows AT&T’s downward trend with new iPhone activations. That almost-vertical, blue line represents the staggering increase in worldwide iPhone sales. Perhaps the US is too saturated with iPhone mindshare and Android clones?

Hopefully the iPhone 5 will shake things up stateside.