There are many countries that do not welcome foreigners with criminal records.
Japan, Australia, Sweden, and even Canada can block entry to those with records. However, the incidences of Canadians being stopped at the American border far surpass that of any other country. This is because the United States is more vigilant and has easy, direct access to the CPIC.
The Canadian Police Information Centre (CPIC) is administered by the RCMP. It is a repository of almost all of the information collected by police forces across the country. United States law enforcement agencies such as the FBI and the Department of Homeland Security (DHS) enjoy full access to these files. If a Canadian is passing through an American border, and their record is known, they may be detained on the spot, or turned back.
Because other countries do not have the same record-sharing through the CPIC, they are much less likely to catch someone with a criminal record at the border.
If a Canadian wants to cross the border into the States when their record is on file, they must apply for an Entry Waiver. If they have a record, but the United States is not aware, then a pardon is advisable. Therefore, it is important to gain a pardon, and expunge your record, before it appears on the CPIC database.