Aircraft carriers were rather important in the Atlantic during WW2, just not the way everybody commonly thinks. Escort carriers (CVE) were vital in the defeat of the U-Boat threat.

A CVE was generally constructed out of a merchant ship hull (either purpose-built or converted), and smaller and slower than the standard "fleet carrier" we're used to thinking of. They carried fewer aircraft, sometimes as few as six or eight, and were considered practically disposable. (Before the CVE was "invented", the Royal Navy added a flight deck to some operating cargo vessels, creating the Merchant Aircraft Carrier... these might have as few as three planes) The CVE was too slow to operate with the fast ships of the battle fleet, but the perfect speed to sail with convoys.

Before convoys had integrated air support, there was a large gap in air coverage between US/Canada and England, which made the job of the U-Boat captains much easier. In that "dead zone" a sub could cruise on the surface without fear of being spotted, allowing them to get into position to ambush a convoy.

Once CVEs started to accompany the cargo vessels, submarines had to be a lot more careful: nothing will ruin a submarine's day faster than a bomb or rocket... or even a strafing run for that matter. Worse still, the submarine really can't fight back effectively against aircraft. Oh, to be sure some German subs carried anti-aircraft guns, but it's hard to submerge and hide when your crew is outside the hull.

CVEs also served in the vital "ferry" role, being loaded with aircraft nose-to-tail and wingtip-to-wingtip. It wasn't glamorous work to be sure, but you can put an awful lot of aircraft on a 500' long flight deck if you don't intend to fly off of it.

US fleet carriers also served in the Atlantic, but for the most part were needed more in the Pacific. Neither the Wasp or the Ranger were deemed fit for service in the Pacific but the less challenging aerial situation in the Atlantic/African theaters was within their abilities. Indeed, I've called the Wasp the worst US carrier in the Pacific. Both carriers were floating design compromises that made them too small for their jobs, and it gives you a sense of the desperate times the US Navy reached in the Pacific that they had to use the Wasp there.

There were some 151 aircraft carriers built in the US during WW2, 122 of them CVEs. Many of those saw service in the Atlantic at one time or another.

If you're interested in knowing more, the books Hunter-Killer and Little Giants by William T Y'Blood are excellent resources. Both are about escort carrier operations in WW2, with the first one covering the Atlantic, the second the Pacific.

Yes. At the entrance of the US to the war three of the six United States carriers were attached to the Atlantic Fleet. The most capable, Yorktown, was immediately transferred to the Pacific while the smaller and more vulnerable Wasp and Ranger remained in the less dangerous Atlantic initially.

Wasp made two separate trips to fly Spitfires to Malta before Yorktown was lost at Midway, at which time she was transferred to the Pacific (and promptly sunk).

Ranger provided close air support to the Operation Torch landings, among other operations, and remained in the Atlantic until being transferred to California to serve as a training carrier very late in the war. She was never used in a combat role in the Pacific.

Some of the new Essex class ships also spent time in the Atlantic, as did a number and variety of smaller escort carriers. The latter were generally used in am ASW role although some also supported the North African landings.

There are any number of sources that will cover this, but I recommend the DANFS on the Navy website as something quickly available and easy to search.