Also note that TMo is officially shutting down 2G (which PM needs for voice roaming in US) in Dec 2022. I believe they've been cutting back on the network already, though not yet shut down completely. PM should probably think about not offering voice roaming any more (text and data roam in US on 4G).
[to correct myself, I've seen lots of estimates of TMO 2G shutting down Dec/22, but haven't found a firm date actually published by TMo]
Roaming isn't part of your plan...you need one of the 10 Day US Roaming add-ons available for use whilst in USA.
Manually select T-Mobile once you have it and are in US.
ah yes...there was an old plan that included US Roaming but looks like you're a new customer. That old plan hasn't been around for a few years now. Only the 10 Day US Roaming add-ons are valid nowaday.
Thanks for the reminder @Yummy