You will need to ensure that whatever qualification you get is recognised in wherever you want to teach.
I am out of touch, but a newly qualified (uk) teacher had to do one year teaching within a set time to go from NQT (Newly Qualified Teacher) to Teacher.
I have no idea of the US system, but their system is State based, Lawyers need to qualify to be recognised at each State Bar that they want to work at. I imagine that qualified teacher status is similar.
Before you commit, you do realise that you can’t just “decide” to move? Apologies if you have a US passport or similar. Qualifying as a US teacher may not help if you end up back in the UK.