Curious, how do you end up at Laguardia on a transatlantic flight? It isn't an international airport -- the only international inbound is from Canada with precl

Curious, how do you end up at Laguardia on a transatlantic flight? It isn't an international airport -- the only international inbound is from Canada with preclearance. I know Shannon in Ireland has preclearance too but didn't know you could fly into LGA.