Hello - I am having the same problem. My data roaming does not work in New York. I am from Canada and got the phone from fido in Winnipeg.
Let me save you some time: airplane mode is off, data is one, roaming is on, i have data left on my plan, there are no data blocks on my account. I have verified the access point settings. I already tried turning my phone on and off. I already tried resetting the network settings.
Having no access to data left my high and dry on my trip. Called 3 times and troubleshooting would randomly work on the phoen for an hour then lose connection to mobile data. Brutal experience.
Welcome to the community
I can understand how difficult it can be when you depend on your phone for work and are not getting access to your data.
From what you mentioned, I see that you have done most troubleshooting steps at this point.
However, I do have another question.
Have you tried selecting another network in the U.S manually?