Lear45XL unnecessarily confused the issue by stating a particular instance in which US Certificates did not meet ICAO standards. It would have been at par with saying saying that Canadian licences do not meet ICAO requirements . . . because in the case of Canadian Recreational Pilot Licence and Microlight Licence, this is not an ICAO licence, etc.
I hold US and Canadian ATP's. If you are a citizen of neither country, I would say that you should find out how each licence is viewed by your home country. The reason for this is that your local Civil Aviation Directorate may favor one over the other. For example, Oman's Directorate General of Civil Aviation and Meteorology (DGCAM) has issues over the way US licences are issued and so does not like the US Certificates except under other qualifying factors.
However, in most other cases, I have come to consider my US Cerificate as a licence to print money. It is more widely recognized, the worldwide N-registered fleet is humongous and the more lucrative contracts call for US Certificates. It is also a easier licence to maintain-- no regular licence validation fees, unlimited validity of both the licences and the Instrument Rating, and FAA medical examiners in almost every country worldwide.
However, neither licence is worth much without significant experience.