Not really, especially because a group of Americans would've been easily detected as they couldn't hide within local communities.

But, there were American/ British soldiers who worked together with local resistance/ Partisan groups and tried to coordinate between regular armies and resistance groups. The success was varying I think. There was also the try to help with armament.

This happened mostly in France, Yugoslavia and Italy. The partisans on Soviet territory mostly were affiliated with the Soviet government and were often trained by them. This isn't as true for nationalist inspired groups as e.g. in Poland.

But if you generally ask about irregular resistance then there were attacks on German forces (used as non-synonymous for Nazis). Yugoslav Partisans freed Yugoslavia by themself mostly without direct help by major Allied powers. (Spoiler) General Partisan warfare was more like the ambush in the woods, and less like the burning theater.

Operation Anthropoid is somewhat similar, though it was focused on killing a specific Nazi - Reinhard Heydrich. Czech agents were flown from the UK to Czechoslovakia, where they successfully killed Heydrich. Well, the plan initially looked like a failure, but Heydrich eventually died of wounds received from a grenade that was thrown at him by one of the assassins, Jan Kubiš, whose Sten gun had jammed.

The aftermath of Anthropoid shows the danger of such missions: thousands of innocent Czechs ended up being killed by the Nazis as reprisal.

The closest thing you will find to specialized units like this would have been "proto-special forces" units.

Early units along these lines included the recently formed Army Rangers, which were elite light shock infantry. The were used in raids, amphibious landings (such as Point du Hoc on D-Day), Dieppe (there were some Rangers there), and other fast action assaults.

The 1st Special Service Force was a combined American/Canadian unit which were trained to be an airborne capable light mountaineering and winter strike force.

Marine Raiders were formed in the Pacific to form quick strike light craft assaults, but were mostly used as infantry.

None of these units were ever really "guerrilla forces" in the sense of a modern SF unit operating independently behind enemy lines. The closest to what you are imagining was actually the O.S.S. or Office of Strategic Services, which serves as a double founding group for the modern concept of Special Forces (The Green Berets) and the Central Intelligence Agency.

The O.S.S. was tasked to be the intelligence force for the Americans during the war. In this capacity, they served as the classic "spy"; infiltrating locations and gathering information, disseminating disinformation, counter-intelligence, developing turn coats, etc. At the same time the O.S.S. served as a force to supply and co-ordinate with the various European resistance forces. In this regard they would supply explosives, radios, "spy craft tools", recover downed airmen. In Indo-China-Burma, they did train and equip indigenous forces that harassed and ambushed Japanese forces in the area.

But were there roving teams of American soldiers wandering France killing Nazi officers? No.