At that point "it's legal in my country" will no longer suffice for anything online (which is basically everything). Everyone will need to be in compliance with the most restrictive subset of the law. Just in the realm of copyright, the public domain would be dramatically curtailed. All you would need is one rich country with strong legal ties to other nations and an appetite for perpetual copyright, and you would have a judgment mill by which you can make using any public domain content extremely risky.
The current status quo of country-by-country blocking may seem silly to people who know how to evade those blocks, but it makes courts happy and walls off the worst effects of copyright maximalism.