What are the implications for carrying across the United States
Welcome to the community @UnionMike
This is a complicated question as you have at least as many differing responses as there are states in the union. I would recommend visiting the USCCA Reciprocity Map or downloading the USCCA Reciprocity App for your phone in order to have a better understanding of the implications based on the specific states you are planning on traveling across.
Bruen was about subjective versus objective standards for issuing carry permits or licenses. It did not address the constitutionality of permits or licenses themselves, nor did it address reciprocity between states or the analog of drivers and marriage licenses as universally accepted (which are not subject to state reciprocity).
Yes it is complicated if you follow it to its logical conclusion the right to carry across the U.S. cannot be infringed by state laws
@UnionMike Welcome to the community
Don’t bring one to New York if you intend to stop