I think that it’s implicit that the volume of Godzilla would increase; we need to assume that the bounding layer has a degree of elasticity and that that the matter displaced by the flotation cavity will expand into that, reducing the net density.
Mighty Godzilla, with power untold Rises through the waves; his powers unfold Hidden muscles in clever design Create a new chamber as they realign
Inflating his body, a titanic display Defying the depths, he floats up and away No long bound by the oceans’s might Godzilla soars, a triumphant sight!
I can’t offer any comparison between the Us and the UK, but I have some experience of having a neurodivergent child in the UK. We live in the NE of England, an area which is on average pretty deprived by UK standards*, however the support from the primary and secondary state schools we have used has been exceptional, with additional staffing as required and sensitive adaptions to needs throughout. There was some bullying at one point in primary school, but that was dealt with promptly and effectively and strategies were put in place to avoid social isolation - things it would never have occurred to me to do. The support for LGBTQ kids in secondary has also been pleasantly surprising - to the point that those who try to pick on trans kids find themselves becoming persona non grata pretty quickly.
There are some pretty huge cultural differences between the UK and the US, as you will know, and I suspect adjusting to those are going to be the primary problem in the move, rather than the support for a neurodivergent or SEN child.
*I feel like I should stand up for my adopted North-East; whilst it’s true that there are deprived areas, the NE is a beautiful place, the people are friendly and welcoming and the cost of living is low compared to many areas. The accents are proper canny too!