Needless to say it would make international relations a little bit more complicated. Major changes include:
The United States now borders a few new countries including Morocco, Mauritania, Senegal and Cuba.
Spain now has a land border with Algeria.
Italy now borders Tunisia.
Greece borders Libya.
Brazil borders a whole bunch of new states from Namibia in the south to Liberia in the north.
India now finds itself in the southern hemisphere, right next to Antarctica.
You could walk from Australia to Tibet (which is no longer attached to China).
While China has lost Tibet it has gained a massive amount of new coast line.