Cat1nthehat will you have the right to work in the US? Are you giving up any kind of career?
Is this a short term "ex pat" move or is it for the foreseeable future?
Do you understand that if you're away two years before DD would go to university she or you'll be paying much higher fees, either US university fees or overseas fees in the UK?
The little Englander accusations are misplaced because most of us saying that this is not something to do lightly with a 13 year old have experience of big moves as older children, or live overseas... This is the living overseas board...
The people talking about learning a new language are ignoring the fact you're moving to the USA not France/ China...! As well as the fact this is no longer as easy at 13 as at 3, the neuroplasticity is not the same and at 13 a new language won't be picked up in the same way a small child does it, but learnt the way an adult does. This is irrelevant for a move to America anyway obviously.
I live overseas and know that emigrating is hard for an adult and children of school age, generally the older the harder. Lots of emigration attempts with an effectively trailing spouse fail because the spouse becomes deeply unhappy especially if they have older children who aren't home with them, are used to working and are not legally (or due to language) able to work in the new country.
This move might work out but there are a lot of variables (if your husband is a very high earner and will have an expat contract an international school will soften the change of school system blow at last, and the financial implications for your DD if she wishes to go to university can be mitigated).
Take her seriously, it doesn't mean you absolutely shouldn't go but she isn't being dramatic - there will be an absolutely massive impact on your 13 year old daughter.