Any phone you buy in Canada for use on any carrier there will have basic technology compatibility with carriers in France but, as you point out, there are differences in the frequency bands that are used. To choose a North American phone the makes full use of the services that French carriers offer requires picking one that supports as many of the bands used in France as you can. Note that phones without full band support will still be useful but you are likely to be less happy with the service you get than your friends with French phones are.
You'll need to read the specifications of the phone you are looking at to determine the bands it supports. Bands were traditionally named for their approximate frequency in MHz (a number between about 700 and 2600), but 3G and 4G bands are usually now referred to by band number, a small integer, since this is less ambiguous. These are the bands I believe you want the phone to support for use in France:
2G (GSM): 900, 1800
3G (UMTS, WCDMA, HSPA): Bands 1 & 8 (2100 & 900)
4G (LTE): Bands 3, 7 & 20 (1800, 2600 & 800)
Of these only LTE Band 7 is also used in Canada. There is also a 700 MHz LTE band starting to be deployed in France whose band number I know not but which I hope is the same as one of the North American 700 MHz bands your phone will likely support.
About frequencies, it is probably worth noting that lower frequencies have longer range. While this doesn't mean that low frequency bands are used more (in fact the opposite is true) it does mean that when only one band is available it is often the lowest frequency band the carrier uses, so support for the low frequency bands may make a significant difference in how well you perceive the phone to work. Unfortunately North American phones supporting LTE band 20 are a bit rare, so you may want to carefully consider this when choosing the phone.
If you buy a phone directly from a Canadian carrier you'll want to make very sure it isn't SIM-locked or can be easily unlocked.