US Presidential Election

I was astounded to see the huge lines of Americans waiting to vote over the last few days. Why is this allowed to happen ? Surely in a democratic society such as the USA claims to be, ensuring not only the right to vote but also the opportunity are both equally paramount. I am over 70 and have voted many times in British elections at all levels, and yet have never had to wait more than a couple of minutes. Why is this not the case in the USA ? Is it because it discourages those most likely to vote democrat ? The Labour party in the UK has always had the same problem - the Tories love it when it rains on election day ! Should voting be made compulsory as in many countries in Europe ? Lots to think about here !