After a few verifications, it does not appear that we have a roaming partnership with Verizon in the US. We do, however, have roaming deals with several other providers, including T-Mobile and AT&T.
If your question concerns CDMA (2G) coverage, fewer and fewer providers support this older technology so we cannot say for certain that it will be supported by the local providers. If your question is about WCDMA (3G/4G) coverage, then the answer is: Yes, you will be able to roam in the US with a Videotron SIM card and an iPhone X as long as there is coverage from any provider we have a roaming deal with.
You may check roaming coverage per country and device model here : https://videotron.com/residential/b/mobile/travel/N-1r4y30r .
Have a great evening!