I’ve had trouble with American Express cards, both registered and un-registered and tend to avoid them now.
I’ve never had problems with Visa or Mastercard cards at any merchant. I’ve always paid with cash and I have never been asked for any identification.
Sure, you can live without the burden of debt, but it’s harder to travel without a credit card.
The reloadable cards usually involve actual credit and, as such, require a social security number to be activated.
I imagine that this depends on how the merchant does their billing.
The cards can be used to fund a new Pay Pal account, which allows us to avoid the final limitation, if the foreign merchant accepts Pay Pal.
And in some areas it’s hard to even rent without a good credit history (it’s not an issue where I live).
However, for my dad, who lives a pretty simple life these days, it could work.