No. Generally speaking, the EU’s rules are about where you’re
coming from,
not your passport. Americans can enter France from anywhere in Europe as well as from the 10 countries approved by the EU. (The EU approved arrivals from 10 countries at the end of July, including Australia; Canada; Georgia; Japan; SKorea; New Zealand; Rwanda; Thailand; Tunisia; and Uruguay).
Again, this is about physical presence,
not nationality. The EU member states do differ as to implementation: France refers to “arriving from” these 10 countries (which most likely means 14 days
at most), Germany requires you to have been “resident” in one of the above 10 countries for at least 6 months. But even that applies specifically to those 10 countries, not if you’re coming from elsewhere in Europe - to include the UK.
So to modify my original answer to
@sergio, the truth is that you don’t even need Canada, entering which will anyways be quite difficult.
The UK allows visitors from the US, though you must self-isolate for 14 days.
Get yourself an AirBNB or something like that for 2 weeks, then you can cross over to Europe with no issues.