Sky Sports has the
UK rights to the series. You can't subscribe to Sky Sports in Canada unless you've got
(a) an exceptionally large satellite dish (to pick up a signal from the very edge of the footprints of the Astra statellites that transmit the Sky Sports channels) ; and
(b) a way of tricking Sky's subscription service that you're in the UK. (There are companies which provide 'proxy' subscriptions for viewers in countries like Spain but I doubt that there's anything similar for Canada).
You can't view Now TV's services outside of the UK unless you've got a UK-based subscription AND you're in an EU country. It
might be technically possible to sign up for a Sky Sports Pass with Now TV and then access their services through a VPN but I certainly wouldn't like to guarantee it.
The Canadian rights to broadcast The Ashes are held by Willow TV. To be sure of being able to watch the games you'd need to look for a satellite or cable provider thar carries their services and then subscribe to an appropriate sports package. Such a provider might well be one that provides services to the USA as well as to Canada. See here for a list of the satellite and cable companies Willow TV has partnered with:
https://www.willow.tv/tvchannel