But I don’t disagree that some EU countries that intend to abuse the GDPR for the purpose of generating massive amounts of revenue from fines may try to make this kind of claim. One of the problems with GDPR is that when you combine unclear regulation with the lack of moral hazard that government agencies enjoy and the financial incentive of massive fines, you create a monster that will constantly seek to expand who and what is covered under it.
Regardless, it’s one more reason to block radioactive EU traffic.
Probably you can offload some challenges to the ad network, if they don't tell you enough of their business, but that's between you and them. For me I'm accessing your site.
You aren’t serving any ads in the case of an ad network. You contracted with an ad network that is within the US and the site on which you served their code is not otherwise subject to the GDPR. Your intent to not serve the EU market is clear.
So while blocking the EU isn’t required, the other tests they use to determine whether or not you intended to offer services to EU residents are a bit murky. In light of that, what better way is there to make your intention to not serve EU users clear to all than to block EU users? That’s the main reason to do it. This kind of blockade will not prevent all EU users from accessing your site, but it doesn’t matter. You’ll have made your intent to not serve EU users clear, which will preserve your immunity to GDPR.
[1] http://www.privacy-regulation.eu/en/recital-23-GDPR.htm