Simple solution.
Make a new EASA rule that intra EASA flights must be operated by EASA licence holders and EASA member state registered aircraft.
It is bloody overdue that we kick the Yanks out of our airspace if they are not willing to allow us the same rights in the USA.
And all you Americans telling us that they are not,performing Cabotage... learn the true meaning of cabotage. it is a flight by an airline belonging to a different zone, performing domestic flights in another economic zone. Schengen zone is one economic area, and is considered domestic for all legal purposes. so your airlines ARE breaking the law.
Now the aircrew performing these flights are just doing their jobs, earning bread on the table. It is at the Political level that we must act, not on our collegues.