My own opinion, they were too expensive and the EV charging network wasn't built up enough to prevent people from feeling like the available range options weren't large enough.

Hyundai has pulled the ioniq 6 but the ioniq 5 and soon to be ioniq3 are sold in the USA still. Unless there was some news I missed. For Kia, Im not sure what their status is.

now both Hyundai and Kia have stopped selling EV models last year solely in the US

They're basically one company and they stopped importing EVs. They still build and sell plenty of new EVs in the U.S., made in their plants in the state of Georgia. They're also currently expanding capacity at their plants, in the hopes of catching more of the growing electric SUV market.

So they no longer sell the top of the line trim level of the Kia EV6, or the Hyundai Ioniq 6, but they're still building and selling very similar models on the same platform. The Kia EV6 still exists in the lower trim levels, and the Ioniq 6N and the Ioniq 5 and 5N, and their smaller EVs (Kia Niro, Hyundai Kona) are still available, too. Both brands launched their 3-row electric SUVs in the US, too (Hyundai Ioniq 9, Kia EV9).

A lot of companies are slowing down their EV rollouts, but I wouldn't say that Hyundai/Kia is the best example of that.

If you are making an ad campaign, all of the US speaks the same language, generally has the same safety regulations, and a much larger percent of the people are your target ad personnel

The EU is a cohesive unit for regulations but speak many different language and once you branch out of the EU to all of Europe you can see why there are huge advantages to advertising in the US.

So no it’s not the absolute number that matters