Actually, DC's tackling this issue right now with the Freedom of Power Treaty started by Black Adam during 52 and OYL in Checkmate, US&FF, and GL.
With the treaty in full effect, heroes that are deemed Americans can no longer enter countries protected by the treaty without their permission (where as before all they needed was UN consent).
Now there's pretty much a metahuman arms race going on (America's attempt at re-creating the Freedom Fighters, before they caught on and went rogue, China's creation of their own super team, The Great Ten, Russia's re-establishment of the Rocket Red Corps, etc).
Heroes pretty much can't just come and go where they please anymore.