The short and long answer is, there's just no other navy that can maintain presence in the same fashion.   Doesn't really have to do with size of the boat, it's a matter of having enough so that: deployments can be conducted while others are in a period of deep maintenance/repair, new aircrew can get qualified for landings (well, not just new- somebody might have a thousand hours but if he's been away at a shore assignment or in school, he'll have to re-qual the same way). entire air wings take time doing workups together just to prepare for a deployment.   And basically since the era between the world wars, the US Navy has been perfecting underway replenishment.   Nobody else can match that ability to get everything from hamburgers to bombs on the fighting ships without having to bring them into port.