I don't know how to degoogle at this point. 90% of my registered accounts across the internet are with my Gmail account because I didn't want them tied to my private email.
If you have the time and are interacting with the account, take the second to change it away from gMail. Insisting on doing them all immediately is setting up a Herculean task that'll almost certainly leave you demoralized. This gets your most-used (and presumably most important) accounts first,and feels much smaller and more manageable.
After 6 (or 18, whenever) months of this you can summon some motivation to change over the last 20 accounts and be done with it.
If the point is to avoid US companies this won’t be useful, but if the point is to avoid Google specifically, it is an option.