From my own research (I'm planning to do this), importing a US spec Tesla to the EU is worth only in very specific cases. You lose your warranty, your vehicle becomes unsupported, and that means SC is or will be disabled, along with other DC charging, according to Tesla unsupported vehicle policy (although I'm sure you can contest the latest, specially in Europe). You lose maps, LTE, and you'll need to adapt yourself the car because Tesla won't. You might also have problems with servicing the car in some service centers (although in principle, according to their gray vehicle/gray market policy, you shouldn't for most repairs). Tesla won't touch the HV system either.
BUT, if you're in the military, there are some exemptions, and for what I've seen, Tesla will make your life easier. The other option that would work is if you're in the US, you got your Tesla very cheap, all or most of its warranty expired anyway, your vehicle is already unsupported (usually this means it was salvage, and usually that's why you got it damn cheap), and you can do the adaptations yourself (which can also solve the problem with LTE). Usually the later means you own an old Model S/X with MCU1, because the MCU2 is quite secure, and you won't be able to do the required configuration changes easily. Then (and only then), it's a lot of work, but doable, and I think worth it. But you MUST live in the US and own the car in the US, otherwise the taxes you'll have to pay when importing the car to the EU will be high enough to make it not worth (if you are a EU citizen relocating to the EU, all the import taxes are waived, providing you owned the car for more than 6 months). So this is a niche case. Anyone that is not in that very specific situation or belongs to the military should consider selling their car and buying something else in the EU. I know that means losing a LOT of money, but there is no other way.
Said that, I don't understand why Tesla is quite against people importing a car they own from other country. It's a hassle anyway, and economically only works if you truly lived in a different country for a while before moving (I mean, the very specific situations I pointed out above). Importing a car from the US while living in the EU is extremely stupid, as you'll pay the same or more as if you bought it directly in the EU and you'll have to deal with all the problems. If Tesla were a bit more open about this, the booming gray market of half-hackers, half-mechanics that make their livings importing Teslas would greatly be reduced.