Invoices from the USA without VAT

I took a number of courses from the USA that were quite expensive. I received a receipt each time and, at my question, an invoice, but my vAT number and so on are not on it. It was all paid from my professional account.

Is this OK or will it be rejected?
Second question: for invoices from the Netherlands, I have to fill in an amount with and an amount without VAT, but they do not charge VAT?

I earn less than £25,000, so I am exempted from VAT.