Yes, with an ICAO IFR plan, you can file to and from the US and within Canada, the Caribbean, Bahamas, and Mexico.
International VFR ICAO flight plans may be filed and will be routed by Lockheed Martin Flight Service to the other country equivalent of the US FSS, but there is no assurance that the flight plan will be accepted.
Many countries have their own requirements and may require fees or manual documentation for flight plans. It is recommended that the pilot contact the local authority for specific information about what is involved in complying with their requirements.
For international VFR flights that cross the US ADIZ, these are routed to the US FSS and must comply with the DVFR flight plan requirements, See the FAQ for DVFR flight plans.
For international flights, pilots should ensure they are in compliance with all rules and regulations governing their flight.