But if OP is travelling between say, NY and LA, that IS wholly within the US. Doesn't matter if he is on RTW ticket, which gives 2 pcs baggage throughout .. which is good for places where the weight system is ie within asia, europe etc. But travelling in economy, *A carriers in the US do not adhere to the 2 free pieces anymore. Whereas in Canada, they still do.

So if you're travelling in the US, as long as you depart from a US city and land in a US city and is not conneting onto an international flight that day, then you are restricted to whatever rules your operating carrier says. And that would mean extra baggage fees. Unless you're *G.

The the Oneworld RTW for example. The ticket allows 2 pieces throughout. But BA's baggage restriction for economy class passengers is 1 piece of bag weighing 23kg max only. Gues what, if you fly on say CX/QF between HKG and LHR, you're allowed 2 pieces. But if you're on BA, the BA bagagge restriction kicks in.