traffic ticket in spain

Your options are to pay it or not pay it. Fighting it would be difficult, since they probably have you on radar/camera (there are lots of those in Spain). You could inquire about it, but it's probably easier just to pay it and be done with it. Whether or not you have had traffic tickets in the US is of no importance. The Spanish ticket won't affect your US driving record.

If you did the crime then pay the ticket. If you didn't do it (and you don't anticipate visiting Spain again) then don't pay it.

Note there are bilateral agreements in place among different countries and Spain by which if you get fined in one you can be prosecuted in the other. Check out whether such agreements do exists between Spain and the US. In any case, as someone put it, if you did the crime better pay up. Also, even if there's no such agreement among those two countries, standing charges can be claimed if you ever come back.

You can also challenge it of course if you feel it's unfair, but it's a cumbersome and lengthy process and not being in the country adds even more difficulty. For the record, it's possible to challenge and win with the Spanish traffic authorities... but one finishes exhausted after so much bureaucracy, LOL!

I'd pay the fine, especially if it's only 50 euros. Seem like a bargain compared to speeding tickets in the US.

... so you know, speeding tickets in Spain are related to the supposedly breach you've committed. Thus, if the speed limit is say 100kph (55mph) and you're 10km over the limit you get a fine (and points are deducted from your license), if 20km a higher fine (and more points), etc... and if the breach is large enough you could have your license immediately suspended and even be jailed. I do believe our license system works differently than yours, over here one starts with 15 points and violations deduct points, when you reach zero your license is suspended.

European countries target rental cars/tourists (ask me how I know) as you aren't likely to contest it = easy money. It's is a fact; no need to go down that rabbit hole again.
Pretty easy money for the rental company too - $46 bucks for a minutes' work; also known as finding money on the sidewalk.

Many opinions about whether to pay or not; several friends got these tickets a couple of years ago, didn't pay and haven't heard a peep since (so much for the US collection agency story) . And some here conflate the topic with some morality issue (i.e. did the crime so do the time) - don't think that was your question.

So, have any non-payers ever been accosted at customs, rental car counter or elsewhere when attempting to re-enter the offended country? Only those who actually have need respond.

Ciao!

Hocap7,
Thank you for taking the time to inquire concerning the legitimacy of the ticket. Having been in the same situation and being able to say "Yep, I had the car at that time and at that place.", I chose to pay the fine. To me the issue is not about the potential threat of collection agencies, or being an easy "tourist target" or even the odds of being banned from returning to the country. The issue is I chose to visit their country and agreed to live by their rules.
So I hope you pay the fine, look past the expense and hassle and then take another trip!
Safe travels!