As of 1 Dec 1941 the US had 7 CVs Yorktown, Lexington, Saratoga, Enterprise, Ranger, Wasp, and Hornet. As of August 1939 the Royal Navy had 5 large carriers and 3 smaller ones they lost 3 by the end of November 1941 but had added 4 more. The IJN on the other hand had 10 but only 6 would be considered fleet carriers I believe. http://combinedfleet.com/cvlist.htm states 7 fleet and light carriers as of April 41. http://www.combinedfleet.com/economic.htm list 6 CVs and 2 CVLs pre Midway. In any case certainly not more than the combined carriers if the RN and USN. Also note that the aircraft compliment of the pre PH USN carrier fleet was roughly equal if not superior to that of the IJN carrier fleet.