In an English speaking county, having a separate surname aids in sorting and presentation of family unities. The character set is typically A-Z. In Spain e.g. one expects a person the have two surnames. The default — but this can be changed – is that first name is from the father and the second one from the mother. By looking at the order of your name you can get information about family structures. Character set is A-Z + Ñ + umlauts and accent marks.
Going to an English speaking country I could expect them to spell my first name correctly; but since it contains a character outside A-Z I change my name to comply with their modus operandi. Yes, their computer system probably supports UTF8, but most people have never heard of this character and you won't find it on their keyboard. No problem, I change my name to comply with their system.
In Spain official forms often expect two surnames and certain characters. No problem, I use an extra hyphen, change my name, use my middle name as a surname or whatever makes the system happy.
Is it perfect? No. Does it really matter? No. So I just respect their customs and get on with my life as a respectful guest in the country where I am living.