In the summer of 1941 the USA was capable of very little more than they did OTL, with the exception (assuming that the Japanese did not attack) of the USN getting involved with more assets and action in the Battle of the Atlantic. The USA could take over the occupation of Iceland sooner, set up basing there for active operations and potentially in the Azores in aid of the naval efforts. You could see some small detachments of the USAAF going to the UK but other than some relatively short range attacks by bombers and adding some fighters to air defense, not much. Under USAAF doctrine you needed a certain mass of heavy bombers for daylight attacks against defended targets to provide the defensive fire - in summer 1941 those numbers were simply not available. As far as ground troops, you might see small detachments going to North Africa, as well as some aviation assets.
The USA in the war against Germany in July, 1941 as opposed to December, 1941 and no war in the Pacific starts the very accelerated US buildup sooner and frees up some resources in the Pacific for transfer to the Atlantic. The reality was that getting boots on the ground in August, 1941 on Guadalcanal and November for TORCH can't be moved up very much. The USA was simply just getting ramped up and trying to equip the forces it had in summer 1941, let alone larger forces. Here, unlike WWI the British (and French) can't give equipment to the US forces to make up for deficiencies