There is a sad dilemma in all of this. Flying on planes and using air conditioning are two factors in high energy use that lead to pollution and global warming, hence the want for air conditioning.
Natural cross-ventilation in hotel rooms rarely happens. Ceiling fans might help. A well devised ventilation system might also help with far less energy consumption than air conditioning; but, retrofitting buildings might be too expensive.
For us, one good reason to travel to Europe has been the pleasant climate. I would like to find a way to keep visiting without destroying it.
I do not hold a lot of hope. I live in a part of the world where evaporative coolers work great at a fraction of the energy use and cost and still most are converting to air-conditioning.
We all need to keep our eyes and minds open to reduced energy alternatives.
Regards, Gary