There aren’t any, you were likely looking at a false ad. Real estate agents are only licensed to work for brokers, they do not work on their own. Brokers licenses, the ones that count, are not only per country, but in the US per state. Many states and most countries will only issue a license to a resident and citizen of that country. There could not be a person with licenses in all countries (many countries the government owns all the land anyway). There are international real estate attorneys, to help businesses with international transactions, but not agents. An international transaction would be handled by the broker anyway, too many legal pitfalls for someone with only a license to work as an agent.
There aren’t any, you were likely looking at a false ad. Real estate agents are only licensed to work for brokers, they do not work on their own. Brokers licenses, the ones that count, are not only per country, but in the US per state. Many states and most countries will only issue a license to a resident and citizen of that country. There could not be a person with licenses in all countries (many countries the government owns all the land anyway). There are international real estate attorneys, to help businesses with international transactions, but not agents. An international transaction would be handled by the broker anyway, too many legal pitfalls for someone with only a license to work as an agent.