Is there an internationally-shared police/intelligence database that countries use to permit/deny entry of foreign nationals?
For example, might France, the UK or the US pool wanted lists incase wanted persons turn-up at international borders?
The Schengen Information System (SIS) is the most widely used and largest information sharing system for security and border management in Europe. SIS enables competent national authorities, such as the police and border guards, to enter and consult alerts on persons or objects. An SIS alert does not only contain information about a particular person or object but also instructions for the authorities on what to do when the person or object has been found. Specialised national SIRENE Bureaux located in each Member State serve as single points of contact for the exchange of supplementary information and coordination of activities related to SIS alerts. At the end of 2017, SIS contained approximately 76.5 million records, it was accessed 5.2 billion times and secured 243 818 hits (when a search leads to an alert and the authorities confirm it).
Schengen borders are interesting, because they are intended to be as frictionless as possible without routine passport control.
SIS is in operation in 30 European countries, including 26 EU Member States (only Ireland and Cyprus are not yet connected to SIS) and 4 Schengen Associated Countries (Switzerland, Norway, Liechtenstein and Iceland).
There are many such databases. Another answer mentions the Schengen Information System, but countries outside the EU and the Schengen area cannot participate. This includes the US, of course, which you mentioned in your question.
Some countries share such information bilaterally. For example, Canadian border officers have access to the United States' National Crime Information Center database.
A more broadly used resource is Interpol. They have several databases, including one of stolen and lost travel documents. They also maintain a system of notices that can include warnings about people who may threaten public safety or who are being sought for extradition. This is the mechanism through which countries "pool wanted lists in case wanted persons turn up at international borders."