If I purchase an iPhone from the USA, will it work outside the county?

You asked about SIM Card. The newest generation iPhones (14 and 15) use only eSim and have no physical SIM card slot. If you live in a country where a physical SIM is required, an US purchased iPhone would be a waste of money. And iPhone Warranty is NOT international, so if you buy your iPhone in the US and then need warranty support in another country, you will likely be denied.

It is ALWAYS best to buy your phone in the country you live and will use it. ANY savings you might see up front, will evaporate quickly and then some if you need warranty support.

Yes, but you'll likely be denied warranty service on it, and if you're referring to an iPhone 14 or above, will need to have a roaming plan or a local carrier which provides eSIM support.

(244770)

There is also some possibility that a U.S. phone might not have the full set of frequency bands offered by carriers in certain countries.

There have also been unverified reports of some overseas carriers refusing to activate SIMs on phones not specifically intended for their country - citing national frequency management regulations.

While unsubstantiated - it’s certsinly a “believable” scenario in certain areas of the World.