Why are covid cases spiking across the US?

Primarily because we have so many people who refuse to social distance or wear masks and party with large groups.

Because the weather’s getting colder and people are refusing to keep their distance and they are partying and violating the protocol. It’s happening at many colleges 

tModerna, Pfizer’s close competitor, announced on Wednesday that it had also reached a point in its late-stage trial that would allow it to begin analyzing data on its vaccine’s effectiveness. Both companies’ vaccines use the same technology, involving genetic material called mRNA, and both went into large trials on the same date in late July. Pfizer’s study has 44,000 participants, and Moderna’s 30,000.

big people living in big cities ..

oh yes 

When I go out in public I see everyone wearing masks. At least inside buildings.

I don't think there's any business that doesn't require masks to enter their building. Some still take people's temperature on entrance.  Most everyone that are not related keep, or try to keep, their respected distance.

 People are out there practicing self-isolation for 2 weeks just because they have a headache or a cough.

 Yet the cases of infection are on an increase.

 So the only conclusion I can see is that masks and distancing is not working at all.

I think its a combination of things. 

First, covid has now moved into areas where it hadn't been, or at least not that strongly before.  These areas tend to be more conservative and so they listened to president Trump who downplayed the severity of the disease and actively discouraged mask wearing, social distancing, and other mitigation efforts.  So people in these states are less likely to take the steps they need to protect themselves and others. 

Second, I think that people in states which had the virus early, and which in some cases sort of had it under control, got complacent.  Some of these people seemed to have thought that the disease was kind of over and that they could slacken up a bit on mitigation efforts.  We can combine this with "covid fatigue" where people are just tired of being cooped up.   A lot of the reporting says that small gatherings are fueling the spread in a lot of places so it seems that people might be taking reasonable precautions in their public life (shopping, working etc) but are taking risks in their private lives. 

Third, we're heading into winter and that means that in large parts of the country it's becoming too cold to do much outdoors.  We know that that the virus has a harder time spreading outdoors than indoors.  But with the exception of a few areas like Florida, Southern California, and the Southwest, it's becoming too cold to reliably do stuff outdoors.  In the places which seemed to have the virus under control, the downturn in infections largely corresponded to the summer, when people could do more outside.  Now that it's getting colder, we're moving inside more and thus getting more infected.

Simple, the  American people  didnt  do  what the  Health  care  EXPERTS  stated  was the  MANAGEMENT  PLAN.

The  American Health care  system  is  one of the  worst in the Western world, totally  profit  driven, for the Insurance  companies!!!!

Trump is the single biggest factor including his counterproductive behavior like rarely wearing a mask. The experts in the field of virology outlined what needed to be done but as usual, trump thinks he know more than he does. The experts said, if the virus isn't contained by the time the weather changes, expect a 2nd wave. People spend less time outside.

They aren't. Too many people have bought into the fake media lies.

Even after the dust clears, the death rate from this so-called "planned-demic" is less than .04% - less than the normal death rate for the common flu (which, by a miraculous turn of events, has the lowest number of fatalities this season).

A connection? Of course - but not to those who'd rather listen to the media and join in the hate campaign against Trump...who, by the same 'miraculous turn-of-events' is being blamed for all of it.

A .04% death rate is not enough to force a mandate on people. It's the well-known 'force compliance against everyone to cater to the few'.

Dump has stopped pretending like he cares.