International phone numbers can be up to 15 digits, but in most places the rules narrow them down further.

For example in the UK the country code is 44, all mobile phone numbers start with 7, with 9 digits after that.

And all US numbers begin with 555, or so I’m lead to believe.

It's absolutely true. All US numbers are 555-xxxx. You can see this in any US movie or TV show, which we know to be very accurate.

Similarly, any time an American car has a fender-bender, or at least one of its wheels leaves the ground, it explodes in a massive fireball.

That's what's really holding me back from getting an American car. Just fearing that somebody might hit my car and then it's over.

Independent of Hollywood, some American cars just might do that. Maybe not in such an impressive manner, but I've been through so many Dodge transmissions and Ford's reputation here is even worse.

joking aside, the 5M figure probably came from targeting like this, such as choosing a few area codes with high tech populations and testing the ~10M phone numbers for each area

Us and Canada, remember we (Canada)helped invent the phone systems

So?