Year of first entry. I count 23 so far, but I'm sure I'm missing a few.
1987: USA, Mexico
1992: The Bahamas, Puerto Rico, Barbados, Venezuela, Trinidad and Tobago, Curacao (Netherlands Antilles), Aruba
1993: England, France, Belgium, the Netherlands, Germany, Austria, Italy, the Vatican, Switzerland, Monaco, Northern Ireland
1998: the Czech Republic
2004: Republic of Ireland