If anything, WW1 happened because there were too many empires rather than a lack of any dominant powers.

Unless you’re suggesting that what the world needs is a single dominant empire? Which would be an odd position to take because history has proven that monopolies are much much worse for abusing power.

Maybe if/when we colonise other planets we can think of the Earth as a single government with countries acting like states (kind of like the EU but with less sovereignty for each state). However that’s only going to happen if we work together and generally cooperation is viewed as counterproductive to empire building. So we come full circle back to my original point.