What were the reasons that the North and South feared each other's influences on the course national affairs?at least 4 to 5 reasons

The North and the South's fears of each other's influence
on the course of national affairs:

The Industrialists of
the North wanted tariffs.  Tariffs artificially raise the price of imports so that
domestic manufacturers can raise their prices too and thus make more money.  It is
legalized robbery.  The people of the South did not like to pay artificially inflated
prices for their goods.

The Industrialists and Merchants of
the North wanted the government to finance improvements to harbors.  The government has
no money of its own; before it can give one party improved harbors, it must take the
money from another party.  The people of the South did not want to pay the cost of
improvements to harbors.

The people of the South perceived
that northern industrialists were bent on acquiring an empire for themselves in Mexico,
the Carribean, Central America, and the South.  To do this, Southerners believed, the
northerners would first abolish slavery so as to bankrup the southern planters; then
they could control the labor and land resources of the South and then move on to Central
America and the Carribean.

The people of the North
perceived that the U.S. Senators from slave states would continue to prevent bills for
tariffs, harbor improvements, and railroads, if they continued to hold half of the seats
in the Senate.  So northerners started agitating to prevent slavery in the territories
so there would be no new slave states, only new free labor states.  The people of the
South saw that not having a Senate evenly divided between the two predominant
political/social/economic interests, but controled by the northern states, would make
the southern states only subordinant, subject provinces of the North.  Southern states
would no longer be equal with northern states in their own country, the
U.S.A.

The southern people were fearful of the turn that
social affairs were taking in the North.  Atheism and Unitarianism were becoming common
in the North; free-love was being advocated and in some cases practiced; socialist
communes were being established; divorce was becoming common.  Some in the South said
that the southern states should seceed from the Union so that these social sicknesses
could not spread to the South. 

In the North, there were
some people who thought the South might gain control of the government and make slavery
legal in all states.  This was not very likely because there were a lot more people in
the North than in the South, therefore the North would always have retained control of
the House of Representatives.  There probably were not many people in the North who
thought this, but Abraham Lincoln thought there were some.  He played on this fear in
one of his political speeches and he would not have thought that he could make political
capital on this fear if he did not know anyone who held this
fear.

On your computer, search for University of Michigan
DeBow's Review.  Within DeBow's Review, search for Python.  The
first two articles on the resulting list are very good about southern perceptions of the
North.  They were published in 1857.  I tried to establish these links below, but they
would not stick.  You may enjoy a short book titled The Kingdom of Matthias: A
Story of Sex and Salvation in 19th-Century America by Paul E. Johnson
& Sean Wilentz.