I think so, only a country with all people in friendship
Resources would be an issue. I think adversity is conductive to some sense of human happiness - a sense of disparity conductive to our ability to feel alive for certain periods in our life. The world without borders would, initially, have issues with the right of human mobility, and strike fear into the hearts of some. It would be interesting to envision how such would pan out over many years. And despite lack of borders governance according to region or smaller localities such as cities is still necessary.
The question may be: do we need to think in teams/compete in order to survive better?
No. To limit itself and other people it is necessary. Otherwise there will be an anarchy. You go out of doors - and any can shoot at you... (