My guess: he want to say "flying to the USA" with LH.
To the initial question: another guess: might depend on your appearance. I would give it a try. But be prepared to have the carry on (not the laptop case) checked in. I had it that they ask you to check in the luggage at the gate. Then they may give you a tag and ask you to leave the luggage outside the plane at the door. You may accept and later remove the tag while approaching the plane.