Whom has not heard about how hard it is to get a visa or visa waiver for the USA and finally to be allowed to enter. Therefore I was keen to find out, which regulations there were. I already thought about to continue to Mexico from the USA and had mail traffic with the border protection officers. I actually had some problems to understand what means entering by a port. I did understand that it was by an airport and even harbour, but what did the regulations say entering the USA by car, bus or walking. Anyway I have got the answer, that I am not allowed to finally leave the USA by bus to Mexico. Like all the other countries before, the USA asks for a flight ticket home (or other country).
Actually it sounds worth as it is and like the Canadian border control says being very hard, I did not have any problems anywhere, also I was going by car between Canada and the USA several times and another time coming back from Mexico, where I have been walking across the border.
Volunteering in the USA is official allowed in any age, but one should not tell the border control, that one will do it. Often the officers do not know about it.
If you will know more about how to prepare an RTW-trip check the New Zealand site: dorotheeinternational.blog/New Zealand/Preparing for New Zealand.