You may have the order initially refused and be account banned, and be required to provide photo ID to support in order to unban it. I’ve read on this sub that this can happen to completely new accounts trying to buy the Deck

Otherwise, no, you shouldn’t have issues, provided you create the account from a US IP address and use a US payment card

I use the Steam Controller constantly to play docked FFXIV and PAYDAY 3. Though I use a Stadia controller for any games that work decently on controller, such as HITMAN 3 and Watch_Dogs