I am actually surprised that short-distance flights aren't taxed more in Western Europe. The train infrastructure in France is world class and can get you from Paris (North-Central part of the country) to Marseille (Southeast), a distance of about 500 miles, in 3 hours. For Americans, this would be roughly equivalent to go from Boston to Washington D.C. (a trip that takes 7-10+ hours)
Is the carbon footprint for train travel significantly lower than for plane travel?
See (for one): https://www.seat61.com/CO2flights.htm