Theoretically, yes, you are right. But some companies are just going to say, oh, you are based in the US, let's look for a different vendor.
It's not even necessarily about the GDPR. For example, US companies tend to send really shitty invoices. There's barely any info on the invoice, some don't even include the full legal name and address of the invoicer. That really sucks when the tax authorities audit you and want proof for where all your money went.
If I buy services from the EU, I can assume that they comply with the GDPR, and I know that I'll get a proper invoice with VAT, and I won't have trouble with the tax authorities.