Excuse me, Mr. Joaquín Báez, the question can a 15-year-old girl travel alone or does someone take responsibility for us until she reaches her destination?
What M Berger says is correct
If it is your port of entry to the USA, you have to collect your luggage after migration, go through customs and then there is a band where you deliver it without having to re-document. From there you go to your final destination. If it is your port of departure you do not have to do anything. It goes straight to your final destination.
They take care of all your luggage
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