Yes, Boost Infinite offers a “North America Connect” add-on for an additional $10/month that offers unlimited talk & text plus 5 GB of cell data. Cell data while roaming in Canada and/or Mexico is not unlimited.
MobileX is working on it. Their approach is said to be data purchased in one country may be used in any other country where MobileX has a carrier partner. Currently, MobileX has one U.S. carrier partner (Verizon) and no publicly known carrier partners outside the U.S.
US Mobile has international roaming that, I believe, is not limited to Canada and Mexico in beta. That said, as of now, US Mobile requires a large deposit of $500 or so to cover unanticipated costs. I don’t see this as a practical offering right now.
Visible offers unlimited talk, text and data roaming in Canada and Mexico but one must upgrade to Visible+ at $45/month.
I don’t get excited about international roaming. Generally, when traveling outside the U.S., I prefer purchasing temporary local cellular service in the country or countries in which I’m traveling. Historically, I’ve found this to provide more bang for my buck than paying a domestic U.S. carrier to roam internationally. Canada, whose domestic cellular market is terrible might be an exception.
Alternatively, I might purchase an international data eSIM from a vendor such as Airalo. Of course, using an eSIM requires one have an eSIM capable phone or maybe not:
I probably need to update it but here’s an article I wrote on international travel when we launched this Community back in November 2022: