(Without being biased towards one party or the other) Why do some states/cities trend extremely Democratic or Republican? (80%/90% Margins) ?

Sometimes people are willing to relocate to be around the likeminded. 

States that cultivate weak people usually go DEM because the DEM's Bribe the poor with free stuff (You just have to accept their sick social agenda).

States that cultivate good working ethics typically go REP , because they are more independent and want Government out of their lives!

Go Utube:"Types of Governments Explained" That should set a NON-Biased political spectrum for you. From an American-US Constitutional point of View!  Which we all should have/understand if we live in America !

Urban areas tend to be more sophisticated and pragmatic. Rural areas more opinionated and traditional. 

While a generally agree with everyone else about the rural areas tending to be republican and the more urban areas being democratic one major thing I don't see mentioned is what I call learned politics from parents, siblings friends and acquaintances. This is where we learn from others what THEY prefer and why BUT in this scenario they don't lean FACTS about the opposing party they learn only what they're peers peers learned from they're peers and they learned from they're peers and on and on and on.without ever learning the TRUE differences. Take for instance in my parents household we NEVER discussed politics although I never asked I assume it was so me and my sister would decide for ourselves what parties we would support or shun and develop out OWN independent opinions and we have. My sister supports primarily the TEA party then the democrat party as a liberal leaning independent and I tend to support independents then the republican party as a conservative leaning independent but we still all avoid discussing politics at family gatherings to keep tensions low due to opposing opinions.

First, there is a tendency of all urban areas to be bluer within each state than rural areas.  Without going into the details which is impossible to do without one side or the other claiming bias, the Democrats are perceived as being friendlier to urban interests and the Republicans are perceived as being friendlier to rural interests.  (There is some misperception there, but, to some extent, it is also self-fulfilling.  When the majority of Republicans represent rural areas, they are less likely to emphasize programs that would benefit the cities, and vice versa).

Second, it flows the first tendency that more urbanized states also tend to be bluer and more rural states tend to be redder.  No state is as blue as most major cities are because all states have some rural areas, and no state is as red as the reddest rural areas because every state has some urban concentration.  (The reddest state in 2020 was Wyoming, but it was only a 70-26 split.  The bluest state was Vermont which was a 66-31 split.)

Third, aside from urban-rural concentration, history has a lot to do with it. There used to be much more state variation within the political parties.  After the Civil Right Act and Voting Rights Act, many Southern Democrats became Republicans, and many New England Republicans became Democrats.  While it was not a majority of New England Republicans or Southern Democrats who realigned, it was enough to flip control of both regions.  There are other key regional events when one of the parties got on the wrong side of a major issue and lost voters coming of age during that time period on a permanent basis.  (See the California Republican Party in the early 90s on immigration.)

Urban area tend to be Democratic - rural area trend to be Republican.  Various rationals but I'm not sure I believe them, so your conclusions are just as likely to be valid as mine.

Health officails are saying that because of bidens failed "biden plan". Up to two million Americans will die of covid19 by the end of the year. biden has no idea what he is doing. 

I think its because people tend to live where they are comfortable. We segregate ourselves more than our government does.