This specific situation is not that, it's a problem with
visa waiver reciprocity: all US citizens get a waiver to the EU, but not all EU countries get waiver in the US. In 2001 the EU adopted a rule that reciprocity is required for an EU visa waiver.
The US were notified about the non-reciprocity issue in 2014 alongside Australia, Brunei, Canada and Japan, published in the Official Journal of the European Union on 12 April 2014[0]. The situation with Australia and Japan had been resolved by April 2016[1], Brunei resolved it in April 2016[2], and Canada is in the process of resolving it and will be implementing reciprocity through 2017 but there had been no such evidence from the US by December 2016[3]:
> Following intensive and coordinated efforts and sustained engagement between the EU and Canada at political and technical level ahead of the 16th EU-Canada Summit on 30 October 2016 in Brussels, Canada provided a clear timeline for achieving full visa waiver reciprocity with Bulgaria and Romania, the two remaining EU countries whose citizens still require visas. On 3 October 2016 Canada announced that it will lift the visa requirement from 1 May 2017 for Bulgarian and Romanian travellers who have held a Canadian temporary resident visa in the past 10 years or who hold a valid U.S. non-immigrant visa. The rest of the travellers will become visa-free as from 1 December 2017.
> Despite the stepping up of political and technical contacts, there have not been comparable indications of progress towards the lifting of visas with the U.S.
[0] http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX...
[1] http://europa.eu/rapid/press-release_IP-16-1345_en.htm
[2] https://ec.europa.eu/home-affairs/what-is-new/news/news/2016...
[3] http://europa.eu/rapid/press-release_MEMO-16-4484_en.htm