What on earth is a 'bumbo'? And is it really essential to have one?

If I now were to move to the USA, I would assume that there is an equivalent or a suitable replacement there of whatever I can find and normally use here. Even if things are cheaper, is it really worth a hassle shipping stuff across the Atlantic all the time?

But if bringing familiar, culture-specific objects makes you feel more confortable and less stressed about moving to a foreign country, then I understand.