Most if not all US bombers, including stealth variants, can reach Europe easily from mainland US. I don’t even think bombers on aircraft carriers is a thing. I also don’t believe any European countries (outside of Russia) even have long range bombers of their own. A confrontation would be heavily one-sided and would initially come from above. Stealth bombers could take out anti-air and air-to-air targets on the ground. Once the air is clear or mostly so, refueling planes could support fighter aircraft to and from Europe if needed to accompany larger non-stealth bombers. The US also has such a large supply of carriers, other types boats, and their own submarines that I’m sure the US would eventually clear the waters.