I always take my own to the States as hiring actually costs more than buying a new one. Only once has one been damaged, flying BA and somehow they managed to snap the top bit off. There were very good though and paid for a new one within approximately 3 weeks. was a bit inconvenient though.
No need to be so narky eldon. I have lived in Australia where there are insurance claims following accidents that haven't been paid because of illegal car seats. What I am saying is that it is against the law in some counties and people have been caught. Unfortunately the hard way which has been following an accident.
We have hired them in various countries, and I had been shown exactly how to tell if a seat was fitted properly by a great fitter over in the UK. I was reduced to tears in Bordeaux airport after trying 3 seats that didn't fit the car we had hired. Eventually one of the porters helped and we found something suitable. We had similar issues in Greece and had to change the car to get any of their seats to fit any of the cars. We have taken seats to the US - but they were boosters and so I assume OK at the time. You need to consider how you would get from the airport with no seat to the place you would buy one from if you decide to buy.
I have rented car seats on holiday in US before and they have been pretty dreadful - and very expensive. Once they just pointed at a pile of battered seats and told us to pick one. Latterly we took boosters with us - but now thankfully they are old enough not to need them. If possible, buying while you are there would be best / cheapest.
I've decided to hire because I don't trust the baggage handling machines not to bash the car seats around - plus the temperature changes in cargo - and compromise them. Getting compensation for a broken car seat is not how I want to spend my holiday!
I think the car seat laws vary by state, but UK seats are not approved for use in the US because they have different testing bodies etc. Depending on how strict the law is where you're going they might turn a blind eye to a UK seat (as long as it's the appropriate "stage") or not even notice, but I think for example some states require seats to have a top tether which is only just coming in here and isn't on all UK car seats yet.
Laws for all states - you'd have to get someone else's opinion on how likely you'd be to get pulled up on the UK seat thing!
Has anyone rented a child car seat abroad and was it successful? We are thinking of taking our own, but worried about it getting damaged in transit/ more to take. We are doing a long trip so will need about x3 different rental car services, so it gets complicated... Our daughter will be 22months at time of travel.