Location Of The Domain Name Server (DNS) Is Important ?

we have a server where we run sites and emails, but now we are going to buy a offsite email solution (based on ms exchange) in order to have our emails running when our web server is down.

But at the momment we run our own dns at our webserver using our own nameservers, in order that our emails keep working during a webserver downtime, we need to host our dns server at another location. So the offsite email company that is based in usa, said to us that they can host our dns at their datacenter in usa.

So i will have a configuration like this:

Webserver >> location: Spain
Mail Server >> location: USA
DNS Server >> location: USA

note: 99% of my website visitors came from Spain

So my question is:

Does it matters in terms of speed/performance having my dns server located in usa?

So in a simple way, will my website will it be fast with the dns located in spain, or having it in usa is exactly the same in terms of speed/performance?