I wouldn't say F1 is endurance race, it is something in between sprint and endurance (approx. 1,5 hours per race). Current F1 engines are able to last about 10 hours working (you can use 5 engines during entire season - 21 races), so they could start in 6h endurance race, but not in 24 Hours of Le Mans.
Besides F1, there is also WEC race in September in Austin. Lots of action going on, advanced technology(LMP1 on level similar to F1), fight for lead and tickets a little bit cheaper than for F1 :)