How do you dial an american cell phone number?

Within North America (USA, Canada, and 18 assorted island nations and territories in or near the Caribbean), you just dial 1 plus the area code and the number; for example, 1-213-555-0123.

On a mobile phone (cell phone), just put a plus symbol before that; for example, +1 213 555 0123

On a landline outside North America, dial YOUR international access prefix (most commonly 00, but many countries use other prefixes), followed by 1, the area code, and number; for example, 00 1 213 555 0123